Full text of "Kilobaud Magazine (November 1978)"

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The
mall Computer
Magazine

T.M

Understandable for beginners . . . interesting for experts

Raster Scan Graphics for the 6800 . . . Part 1: the hardware

World of the Brass Pounders . . . receive Morse code the easy way
Kilobaud Klassroom ... No 14: parallel and serial I/O ports

Point of Sale/Inventory Control System for 8080s
Financier/Mortgage with Prepayment . . . from instant Software
Hey, Kids! It's "Mickey Modem"! ... not a toy

Do It with a Kimsi! . . . KIM expansion the easy way
The Remarkable Apple-ll ... a fun machine, plus
Universal Number Converter . . . touches all bases
Hexadecimal Memory Dump . . . painless

IC Testing ... a complete system

Music, Music and More Music ... it hath charms
Build a Serial-to-Parallel Converter. . . a snap

Expansion Time! . . . S-100 memory for SWTP system
What Is a Bus? . . . climb aboard for the answer
wuiiam l Coisher 98 Lucas' Puzzle . . . solution can be tricky

Jay Kuca 100 Home Brewing in Style . . . with solderless breadboarding

Thomas £ Hutchinson 108 Modify Your COSMAC Elf . . . for a little pelf

James Gross 114 Loop the Loop . . . iteration techniques explained

David Koh, M.D.

Robert L. Kurtz

Peter A. Stark

Jfl Bruce A. Barker

D. Borland

Stephen Gibson

Rick Grossman

Robert J. Bishop

Easton Beymer

Cal R. Rasmussen

Douglas A. Schwab

Rod Hallen

F. R. Ruckdeschel

Mitchell, Phil Poole

Erich A. Pfeiffer

Publisher's Remarks— 6, Around the Industry— 7, New Products— 8, Legal/Business Forum — 14, The
BASIC Forum— 15, Books— 18, Troubleshooters' Corner— 19, KB Club Calendar— 21, Letters— 22,
Kilobaud Classified— 118, Contest!— 118, Corrections— 128, Dealer Directory— 143

SBJIS?

40K Bytes RAM Memory

1 ,200,000 Bytes Disk Storage

Desk with laminated plastic surface

DOS and BASIC with random and sequential files

TERMINAL— Upper-Lower case and full control character decoding

SOUTHWEST TECHNICAL PRODUCTS CORPORATION

219 W. RHAPSODY

SAN ANTONIO, TEXAS 78216

More and more, you see the North Star
HORIZON computer at work: in busi-
ness, research, and education. Its high
performance qualifies the HORIZON
for demanding professional applica-
tions. Over 10,000 users during the
past two years have proven that North
Star hardware has the reliability
for day-in, day-out computing. The
HORIZON is now a serious candidate
for any small system installation.

SOFTWARE IS THE KEY
TO HORIZON MATURITY

North Star BASIC and DOS have been
used to develop hundreds of com-
mercial program packages. These
packages establish that North Star
software has the completeness and
convenience necessary for serious
program development. Because of the
many independent vendors offering
software using North Star BASIC and
DOS, the HORIZON owner now has
the widest selection of software in the
microcomputer industry! Software
available includes: word processing,
general ledger, accounts payable/
receivable, mailing list processing,
inventory and income tax prepar-
ation. Program development systems
such as assemblers, debuggers,
editors, PILOT and FORTRAN are
also available.

EXPAND YOUR HORIZON

The basic HORIZON computer in-
cludes a Z80 microprocessor, 16K
bytes of RAM memory, an I/O interface
and one Shugart minifloppy disk drive.
The HORIZON can be expanded to 60K
bytes or more of RAM, three disk
^^ drives, and three I/O inter-

faces. Performance
can be enhanced by
the addition of the
North Star hardware
floating point board.
Also, S-100 bus pro-
ducts from other
manufacturers may
be used to expand
the HORIZON.

For more informa-
tion, contact your
local computer store.

North * Star
Computers

2547 Ninth Street
Berkeley, California 94710
(41 5) 549-0858

Ohio Scientific has made a major
breakthrough in small computer technology
which dramatically reduces the cost of per-
sonal computers. By use of custom LSI
micro circuits, we have managed to put a
complete ultra high performance computer
and all necessary interfaces, including the
keyboard and power supply, on a single
printed circuit board. This new computer
actually has more features and higher per-
formance than some home or personal
computers that are selling today for up to
$2000. It is more powerful than computer
systems which cost over $20,000 in the
early 1970's.

This new machine can entertain your
whole family with spectacular video games
and cartoons, made possible by its ultra high
resolution graphics and super fast BASIC. It
can help you with your personal finances
and budget planning, made possible by its
decimal arithmetic ability and cassette data
storage capabilities. It can assist you in
school or industry as an ultra powerful
scientific calculator, made possible by its
advanced scientific math functions and

built-in "immediate" mode which allows
complex problem solving without program-
ming! This computer can actually entertain
your children while it educates them in
topics ranging from naming the Presidents
of the United States to tutoring trigonometry
— all possible by its fast extended BASIC,
graphics and data storage ability.

The machine can be economically ex-
panded to assist in your business, remotely
control your home, communicate with other
computers and perform many other tasks
via the broadest line of expansion acces-
sories in the microcomputer industry.

This machine is super easy to use
because it communicates naturally in
BASIC, an English-like programming lan-
guage. So you can easily instruct it or pro-
gram it to do whatever you want, but you
don't have to. You don't because it comes
with a complete software library on cassette
including programs for each application
stated above. Ohio Scientific also offers you
hundreds of inexpensive programs on
ready-to-run cassettes. Program it yourself
or just enjoy it; the choice is yours.

■ * »w

Ohio Scientific

offers you this remarkable
new computer two ways.

DBIIGBII

Z*e .*•* ***■ **» <— ~« ■

B'HIIGBDG

Superboard 1 1 $ 279 Challenger 1 P $ 349

For electronic buffs. Fully assembled
and tested. Requires + 5V at 3 Amps
and a video monitor or TV with RF
converter to be up and running.

..Standard Features.

■ Uses the ultra powerful 6502 microprocessor

■ 8K Microsoft BASIC-in-ROM

Full feature BASIC runs faster than currently available
personal computers and all 8080-based business com-
puters.

■ 4K static RAM on board expandable to 8K

■ Full 53-key keyboard with upper/lower case and user
programmability

■ Kansas City standard audio cassette interface for high
reliability

■ Full machine code monitor and I/O utilities in ROM

■ Direct access video display has 1K of dedicated memory
(besides 4K user memory), features upper case, lower
case, graphics and gaming characters for an effective
screen resolution of up to 256 by 256 points. Normal TV's
with overscan display about 24 rows of 24 characters;
without overscan up to 30 X 30 characters.

Extras

■ Available expander board features 24K static RAM (addi-
tional), dual mini-floppy interface, port adapter for printer
and modem and an OSI 48 line expansion interface.

■ Assembler/editor and extended machine code monitor
available

Fully packaged with power supply.
Just plug in a video monitor or TV
through an RF converter to be up and
running.

.ORDER FORM

Order direct or from your local Ohio Scientific dealer.

□ I'm interested. Send me information on your:
□ Personal Computers D Business Systems

□ Send me a Superboard II $279 enclosed
Send me a Challenger 1 P $349 enclosed

D Include 4 more K of RAM (8K Total) $69 more enclosed

Name

Address

City.

State.

-Zip-

Payment by: BAC (VISA)

Credit Card Account #

Master Charge

Money Order

Expires

Interbank ^(Master Charge)

Ohio Residents add 4% Sales Tax

TOTAL CHARGED OR ENCLOSED

All orders shipped insured UPS unless otherwise requested FOB Aurora. OH

Interested in a bigger system? Ohio Scientific offers 15
other models of microcomputer systems ranging from
single board units to 74 million byte hard disk systems.

America's Largest Full Line Microcomputer Company
1333 S. Chlllicothe Road • Aurora, Ohio 44202 (216) 562-3101

UBLISHER'S
REMARKS

Wayne Green

The S-100 Mystique

When Mits came out with their
100-line bus there was a lot of
bitching. Connectors were very
expensive; it had more lines than
were actually needed; it both
generated radio hash by virtue of
being wide open and it was very
susceptible to interference from
radio or other noise. In general, it
left a lot of unhappy engineers.

Then came Imsai and their
pseudo-Altair, also using the
100-line bus. Then PolyMorphic,
Processor Tech, S.D. Sales, God-
bout, Seals . . . and the first
thing you know we had a stan-
dard: the S-100. This was one of
the better things that happened to
microcomputing because it made
it possible for many small firms
to design interface boards that
would work with a wide variety of
systems . . . providing music,
graphics, art, telephone intercon-
nect, speech, voice recognition,
plotting, control of high-power
devices, etc.

The time it would have re-
quired to custom design each of
hundreds of interface boards to
fit each new microcomputer
system brought out would have
put board prices out of sight and
thus allowed the support of only a
very few systems.

The first to fight this standard-
ization was Sphere, and this un-
doubtedly contributed much to
their collapse. Then came The
Digital Group. Is there any
serious question that their refus-
ing to use the S-100 bus held their
sales down substantially? Only
the very limited accessories they
themselves provide are available
to expand a system. This is ter-
ribly limiting.

Why would a firm oppose the
S-100 bus structure?

Since most of the original com-
plaints against the bus have been
taken care of, the main reason for
not using the standard bus today
seems to be the manufacturers'
desire to force customers to buy
their peripherals and not be able
to use those of other firms.
Depending on which side of the
pocketbook you are on, this can
be explained as practical
marketing or greed.

First, in case there are some
new readers who are not really
sure what a bus is, a few words on
that. Most electronic equipment
is designed linearly, with perhaps
a very weak oscillator generating
a signal at one end, going through
many steps of amplification and
modulation, finally reaching the
antenna. About all the many
stages in these systems have in
common is a power supply, so the
bus is simple . . . plus and
minus. Computers are generally
built around a whole set of inter-
connecting wires (a bus) and each
of the stages involved plugs into
this bus. Signals sent over the bus
turn on or off each of the
modules. Thus it is possible to
have a video terminal, a printer, a
cassette tape system and several
other input/output devices all
connected to a computer and all
sharing the same wires. (For more
information about buses, see
Erich Pfeiffer's article on p. 94.)
The S-100 complaints were
loud and bitter at first . . . and
rightly so. The Altair system just
barely worked (on a good day)
because this bus system was so
noisy. Often, by the time you got
out toward the end slots of a
motherboard, things would go
berserk.

Gripes about connector prices
dropped off as more and more
systems used the 100-pin
monster. Costs of production
generally drop about 15 percent
for every doubling of production,
so S-100 connector prices
dropped and dropped, eventually
bringing them below those of
much smaller connectors. So
much for that beef.

George Morrow and Harry
Garland tackled the noise prob-
lems and both came up with nice-
ly designed motherboards that
were well shielded and greatly
tamed the wild bus. Morrow's is
in his Thinker Toys Wunderbus
and the Godbout motherboard,
which he also designed . . . Gar-
land's is in his Cromemco sys-
tems.

George also came up with a
dandy termination scheme (also
in the Extensys) that helped keep
signals from bouncing back and
forth on a bus line. These evolu-
tions of the S-100 made it possible

to greatly extend the upper fre-
quency limit for the system,
allowing it to work with the
higher speed Z-80 systems.

The S-100 bus is far from
perfect, yet it would not seem to
have any serious disadvantages as
compared to a 40-, 44- or 50-pin
bus. Higher frequency signals
will eventually mean stripline
techniques or coax systems, not
fewer lines. The S-100 has room
for further growth, a feature sad-
ly missing from most other bus
systems. And who knows what
interface someone will invent
next month and the external
cables it will have to use because
the bus had standing room only?
When The Digital Group
decided not to use the S-100 bus it
was because they wanted to try to
be the sole suppliers of hardware
for their system. Ohio Scientific
had the same idea in mind . . .
carrying this one step further by
refusing to give out information
to anyone on the signal timing on
their bus. This seems to have
worked since there are few (if
any) OSI-compatible accessories.
This means that the owners of
OSI equipment have to wait for
OSI to engineer and bring out all
I/O boards ... for music, art,
telephone interconnect, etc. Thus
the work of a hundred small com-
panies has to be tackled by the
mainframe manufacturer ... a
formidable task.

With perhaps 90 percent of the
systems on the market S-100
oriented— and that's the way it
was in the summer of 1977 — the
nonstandard bus systems were
having a very difficult time. Then
came the Heath H8 and their own
bus system. Heath agonized over
this and was relieved to hear that
Commodore had avoided the
S-100 bus with their PET. Actual-
ly, Heath celebrated a bit early on
that one since their kit systems
were hobbyist oriented and the
PET was not.

It would surprise me if Heath
wouldn't have sold many millions
of dollars' more of H8 systems if
they had gone the S-100 route. It
wouldn't have made that much
difference in PET sales. The ap-
pearance of the Radio Shack
system with still another bus,
though it may have comforted
Heath, did not help Heath sales.
As we approach the end of
1978, with TRS-80 sales greater
than those of all other systems
combined, there is some reason to
wonder if the TRS-80 bus system
may not become the de facto
standard. Maybe. For some
reason the small manufacturers
have been slow to adapt to this
new bus. Perhaps they have not
recognized the wallop of the

TRS-80 on the market. Perhaps it
has been the usual engineering
delays. But at this time, the S-100
is still the best bet for someone
who wants to be able to use a
system for a large number of pur-
poses.

Radio Shack has a TRS-100
board coming . . . supposed to
be out in September. This will
plug into an S-100 motherboard
and let you run S-100 I/O boards
with your TRS-80. When this is
out it could change everything
and re-emphasize the importance
of the S-100 system . . . and save
an awful lot of time and money
on re-engineering boards to work
with the TRS-80.

With Radio Shack and their
100,000 TRS-80 systems added to
the S-100 bus line, times may get
rougher for maverick bus systems
such as the Apple, Heath, OSI,
SWTP, etc.

Any arguments?

What Is TI Up To?

Despite Pentagon-like security
measures, word has been seeping
out about the new Texas In-
struments project. Of course, as
with any tight security matter,
there is always the likelihood of
bum dope being passed along to
confuse things.

At any rate, it does appear that
TI has a 16-bit microcomputer
based upon the 9900 chip being
readied for consumer sale. This
will be selling for under $300,
complete with its keyboard and
BASIC. There is a strong
possibility that it will also support
PASCAL, which is a matter of
policy with TI.

The 9900 microprocessor has
not seen much use in microcom-
puters so far, so many com-
puterists are not all that aware of
its possibilities. This chip is par-
ticularly well suited to interfacing
with the outside world and should
be a natural for controlling
things. It has a register that is able
to keep track of time without in-
terfering with other operations of
the system. It also has the ability
to sit dormant, drawing very little
power until an interrupt starts it
in action.

Although there has been little
use for the benefits of a 16-bit
processor in microcomputing ap-
plications so far, the extra speed
of the 9900 certainly is not going
to hurt. Remember that an 8-bit
processor must take two cycles
for the address and one for data,
while the 16-bit system addresses
in one cycle and loads or retrieves
two bytes in one cycle . . . which

adds up to about six times the
work in the same time.

More Tutorials Needed?

A recent letter from a software
service offering I'm not sure what
pointed up the need for more
tutorial articles on the fundamen-
tals of computers. Many of us
have a long, long way to go
before we can even read the ads
and understand what is being of-
fered.

Just to break the accepted com-
puter code of ethics and offer a
specific example of what I'm
talking about, this letter is offer-
ing APL (or APL.SV) as an inter-
preter because of its dynamic
allocation properties. Huh? Then
it helpfully goes on to offer
PASCAL and informs me that
traditionally PASCAL is im-
plemented in the language of a
pseudo stack machine. Golly, I
didn't know that!

Then the letter suggests that
perhaps I need a disk operating
system with virtual memory map-
ping. Would that put an end to
my troubles? Will I ever find out?
Even more exciting is the offer of
an assembler generator that
would allow me to generate
families of assemblers . . . and
this gem includes recursive
macros.

The letter was enthusiastic, so
it may well have a cornucopia of
wonders for me ... if only I
knew what it was talking about.
Let's get some articles written

that will help us decipher this
gobbledygook. It only takes a few
paragraphs to explain these
esoteric terms and give specific
examples that all of us can relate
to our experience. The sad part is
that the writer of the letter was
unaware that he was unreadable.

PET Papers

At one time I hoped I would be
able to publish enough informa-
tion about each system available
so there would be no need for
user groups and their newsletters.
That was when there were only
two or three computer systems.
Today, with four major news-
letters devoted to the PET, such a
concept is obviously ridiculous.

There is just far too much infor-
mation to exchange.

We have the "PET Gazette,"
already in issue #4, running 40
pages. The address is 1929 North-
port Drive, Room 6, Madison WI
53704. The subscription is free.
Then there is "The PET Paper,"
Box 43, Audubon PA 19407, at
$15 for ten issues ... 30 pages
last issue. Also "PET Users
Notes," Box 379, South Bound
Brook NJ 08880. There is some
ambiguity on the address, so
write before sending money.
Another is "SPHINX," running
19 pages last issue and existing on
donations. Write Milt Lee, 1348
Rudgear Rd., Walnut Creek CA
94596.

These newsletters let you know
about available software, hard-
ware, modifications, fixes for
problems, pertinent books, etc.

Reader Responsibility

One of your responsibilities, as a reader of Kilobaud, is to aid
and abet the increasing of circulation and advertising, both of
which will bring you the same benefit: a larger and even better
magazine. You can help by encouraging your friends to sub-
scribe to Kilobaud. Remember that subscriptions are guaran-
teed—money back if not delighted, so no one can lose. You can
also help by tearing out one of the cards just inside the back
cover and circling the replies you'd like to see: catalogs, spec
sheets, etc. Advertisers put a lot of trust in these reader re-
quests for information. To make it even more worth your while
to send in the card, a drawing will be held each month and the
winner will get a lifetime subscription to Kilobaud*

The above notice tells the story. This month's winner of a
lifetime subscription to Kilobaud is M. Bernstein of Cambridge
MA.

AROUND

THE 1N1HJSTRY

Radio Shack To Open 50
Computer Centers

Radio Shack plans to open 50
computer sales and service stores
in 1978-79. "While some will be
located within new or existing
Radio Shack stores, most will be
separate entities and all are ex-
pected to be in major markets,"
said Lewis Korn field, president
of Radio Shack.

"They will be called Radio
Shack Computer Centers, and

their purpose will be to assist area
Radio Shack stores in answering
computer questions and closing
sales, and to develop quantity
sales, principally of Radio Shack
TRS-80 microcomputer systems
and peripheral equipment, to
businesses and institutions.

"The stores will provide mar-
ket area service on Radio Shack
computer products, thus extend-
ing to nearly 100 the number of
service facilities operated by
Radio Shack in this country, and
will include classroom areas

where the company can teach
computer use and programming
to its customers and prospects."

In addition, the new Radio
Shack Computer Centers will dis-
play and sell "a variety of pieces
and parts, as well as packaged
software and, possibly, hardware
items of makes other than Radio
Shack," Kornfeld continued.

"In respect to the significant
number of TRS-80 personal com-
puters we have sold, we believe
the time is right to quickly expand
our ability to keep them in top
working order and provide solid
local know-how for our custom-
ers and employees alike.

"We have converted the former
Tandy Computer store, located
in Fort Worth, into a Radio Shack
Computer Center, and are in the
process of indentifying the other
49 or so cities and exact locations.

"To date we have selected our

(continued on page 128)

kilobaud

Publisher/Editor
Wayne Green

Executive Vic* President

Sherry Smythe

Assistant Publisher/Editor

Jeffrey D. DeTray

Managing Editor

John Barry

Editorial Assistants

Dennis Brisson
Susan Gross

Administrative Assistant

Dotty Gibson

Production Department
Manager:

Lynn Panciera-Fraser
Staff:

Craig Brown
Gayle Cabana
Robert Drew
Bruce Hedin
Carl Jackson
James Lamothe
Dion Owens
Noel R. Self
Robin M. Sloan

Typesetting

Barbara J. Latti
Mary Kinzel
Holly Walsh

Photography

Bill Heydolph
Tedd Cluff

Associate Editors

Tim Barry
Bob Buckman
Ronal Burris
Sheila Clarke
Rich Didday
Phil Feldman
Steve Fuller
Doug Hogg. PhD
Tom Rugg
Peter Stark

Bookkeeper

Knud E. M. Keller

Marketing

Robert LaPointe
Judy Waterman

Circulation

Pauline Johnstone

Customer Service

Joyce Tarr

Receptionist

Denise Loranger

Computer Programming

Ron Cooke
Richard Dykema
Steven Lionel

Micro Lab

Cida Teixeira
Alan Anderson
Lorraine Blakesley
Scott Spangenberg

Mailroom

Bill Barry
Ethan Perry
Michele Walsh

Advertising

Marcia Stone
Nancy Ciampa
Helene Sandquist
Bill York

European Marketing Dir.

Reinhard Nedela

Australian Distributor

Kathenne Thirkell

Kilobaud is published monthly by 1001001, Inc..
Peterborough NH 03458 Subscription rates in the
US and Canada are $18 for one year and $36 tor
three years. In Europe: Kilobaud erscheint mon
tatlich bei Fachzeitschriftenvertneb Monika Nedela,
7778 Markdorf, Markstr 3 Abonnement DM 70. plus
Porto 7 20 ♦ gesetzl MWST; Sfr 81 plus Porto 7.20.
Australia: For subscriptions write — Katharine
Thirkell, Sontron Instruments, 17 Arawatta St.,
Carnegie, Vic 3163 Australia Please write for other
foreign rates Second-class postage paid at Peter-
borough NH 03458 and at additional mailing offices.
Publication No 346890 Phone 603-924-3873 Entire
contents copyright 1978 by 1001001, Inc. INCLUDE
OLD ADDRESS AND ZIP CODE WITH ADDRESS
CHANGE NOTIFICATION

^ NEW

Products

If you are looking for an S- 100
bus mainframe without frills, sol-
idly built and ready to go, take a
look at Integrand Research Cor-
poration's Model 800 Miserly
Mainframe. These enclosures
come complete with a 15-slot
motherboard (connectors option-
al), plastic card guides, a choice
of two different capacity power
supplies, fan, line cord, fuses,
EMI filter and front panel power
and reset switches. The Model
800 comes in desk top and rack
mount versions, with an option
of two color schemes (light blue/
dark blue or beige/brown).

The entire unit comes assem-
bled, wired and tested. The power
supply is dismounted after testing
and shipped in a separate con-
tainer via UPS. Reassembly con-
sists of mounting the power sup-
ply and plugging it into two
wiring harnesses.

The chassis is constructed of
heavy gauge aluminum, to which
high-quality industrial enamel is
spray-painted. Interior surfaces
are coated with an irridite finish
to resist oxidation .

In the rack mount version, the
Miserly Mainframe is priced at
$200; the desk top version costs
$235. The heavy-duty power sup-
ply option, which includes a 110
cfm fan instead of the standard
70 cfm fan, is $85. The standard
power supply is conservatively
rated at 15 A; the heavy-duty
power supply will easily handle a
load of 30 A. Both ratings are for
the 8 V dc line. Integrand Re-
search will install 100-pin con-
nectors for $6 each, or you can
buy them for $5 each and install
them yourself.

Other options provided include
rear panel cutouts for EIA-type
DB-25 connectors. The first four
are standard; the next eight cost
$2 each. They will also provide a
voltage monitor board ($30)
which generates a relay closure
when the ac supply level falls be-
low predetermined limits (great
for driving an interrupt to stop
processing during power fluctua-
tions, or whatever!).

The extras that are included in
the basic price of the Miserly
Mainframe, coupled with the fact

Edited by Dennis Brisson

that it comes assembled and
tested, make it the most cost-
effective S-100 bus enclosure
I've seen. Add to that the options
that are available and floppy-disk
drive covers, cabinets and power
supplies, and you have the most
attractive basis for a system on
the market. After they did all that
for the S-100 bus, they went one
step further and added an SWTP-
compatible motherboard. Fan-
tastic!

For more information, or to
order, contact Integrand Re-
search Corp., 8474 Avenue 296,
Visalia CA 93277, (209) 733-9288.

Ron Burris
Associate Editor

Double and Quad Density

North Star Computers, Inc.,
announces development of a new
controller board that can record
in double density on the new
Shugart SA-400L (single-sided,
double density) and SA-450
(double-sided, double density)
minifloppies. The controller
board formats the SA-400L for
180K bytes (ten 512 byte sectors
on each of 35 tracks) and the
SA-450 for 360K bytes (same as
SA-400L, but with two sides).
Thus, a three-drive system with
SA-450 minifloppies can access
more than a megabyte on-line.
North Star's double and quadru-
ple density expands the perfor-

mance and information storage
of the North Star Horizon com-
puter and Micro Disk System. A
quad density (SA-450) version of
the North Star Horizon and MDS
systems will be available in Jan-
uary 1979. This quad version will
be offered for $200 additional or
$1799 for Horizon- 1 kit and $899
for MDS-A kit. Additional drives
for quad capacity will be $499.

The new controller board can
control any combination of SA-
400L and SA-450 drives in single
density or double density. It can
read diskettes previously written
in single density. Also, it permits
the attachment of single-density
SA-400L drives previously ac-
quired for the original North Star
systems.

North Star is upgrading its
popular BASIC and DOS to ac-
commodate the increased capac-
ity and the performance of the
SA-400L and SA-450 disk drives.
Programs developed on the origi-
nal single-density North Star
software will run in double densi-
ty with little or no change. A
quad capacity additional drive
may be added to a double-density
system at any time.

North Star Computers, Inc.,
2547 Ninth Street, Berkeley CA
94710.

Arian System for
North Star Disk

The Arian Assembly Language
Programming System is designed
specifically for North Star Disk
users. With Arian, you may save
and load both source and object
files to disk. With Arian's dy-
namic file creation, saving a pro-
gram is simply a matter of typing
'SAVE <FILENAME>\ Arian
creates the file on disk if it does
not already exist and saves the
program. From Arian, you may

list the disk directory (DDIR),
rename a disk file (DNAM),
delete a disk file (DDEL) and re-
cover a deleted file (RCVR).

Editing is a breeze with Arian's
input line editor. You may enter
text (without the need for irk-
some line numbers), insert (INS)
and find a string (FIND). Intra-
line editing is supported by a full
complement of features: skip to
end of line, insert characters,
delete characters, replace (direct
substitution) and press the space
bar to move character by charac-
ter through the line.

Arian also supports many ca-
pable features and subroutines
which are nested inside and are
callable by the user. Arian main-
tains two separate symbol tables
— one for the system and one for
the user. However, the user may
use the system symbols without
restriction. The system supports
redirectable I/O, conversion of
ASCII to hex, and vice versa,
print a line of text, output a CR,
call the input line buffer, plus
many others. Up to eight break-
points can be used at one time,
and all registers are preserved.

A special feature of Arian is its
'CUSTOM COMMAND' capa-
bility, by which you may define a
command, name it and then call it
simply by typing the command
name. This is especially useful if
you are testing programs. The
price ($50) includes one disk and
a 51 -page User's Manual.

Supersoft, PO Box 1628,
Champaign IL 61820.

The S- 100-( ompatible AIB

The AIB (analog input board)
is an S-100-bus-compatible ana-
log input subsystem that accepts
multiple low-level analog signals,
multiplexes and converts to digi-

North Star's new controller board.

SL 's analog input board.

tal format with 12-bit resolution
and throughput rates up to 8
kHz. The standard AIB accepts
eight differential/ 16 single-ended
inputs and is optionally expand-
able to 16 differential/32 single-
ended.

Other AIB options include
computer programmable gain,
4-20 m A current inputs and super
low drift. The AIB is priced at
$495 in small quantities and de-
liverable within 30 days.

Signal Laboratories, Inc., 202
N. State College Blvd., Orange
CA 92668.

Interpreter for the 8080
and PDP-11

An interpreter for a subset of
the C-structured programming
language, which runs on both
DEC PDP-1 1 and Intel 8080 pro-
cessors, is available from Tiny-c
Associates, PO Box 269, Holmdel
NJ 07733. The tiny-c Owner's
Manual includes a complete ref-
erence description of the lan-
guage, a tutorial walkthrough of
a training program, lots of sam-
ple programs, including com-
ments on their programming
style, and a description of the
Program Preparation System. It
also includes commented source
code listings of both the 8080 and
PDP-11 interpreters and a chap-
ter on how the interpreter works.

Tiny-c, intended primarily for
the education and hobbyist mar-
kets, handles integer and charac-
ter data and arrays of either type.
Other features include compound
statements, if-else and while
statements, global and local vari-
ables, pointer variables and func-
tions which may have arguments
and may return results. Recur-
sion is allowed. The interpreter
also recognizes calls to functions
written in machine language.

Tiny-c cornucopia.

These, too, may have arguments
and return results. A minimum of
16K bytes of memory is recom-
mended to run tiny-c.

The package includes a Pro-
gram Preparation System (PPS)
with which the user can write,
edit, run, debug, store, recall and
link tiny-c programs. The PPS in-
cludes a standard library of tiny-c
software tools. The PPS is writ-
ten in tiny-c; thus, it serves as an
example of a significant use of
tiny-c and is also easily adapted to
a user's or operating system's re-
quirements.

The Owner's Manual is avail-
able for $40; machine readable
copies of the interpreter are avail-
able separately on several for-
mats of tape and disk.

Dual Floppy-Disk System

Dual-Stor, a fully integrated,
dual floppy-disk system designed

Vector Graphic's Dual-Stor.

The NewO Writehander.

specifically for microcomputer
systems, comes complete with
controller and dual floppy-disk
drive in a cabinet that matches the
Vector 1 microcomputer. The
Dual-Stor disk system has a stor-
age capacity of 243 K bytes per
8-inch diskette and utilizes the
standard IBM-compatible re-
cording format. Using pro-
grammed data transfer, the Dual-
Stor operates with both static and
dynamic memories at a data rate
of 250K bits/seconds.

Completely compatible with
the S-100 bus, the disk system
features the Reset-and-Go func-
tion on power up. Other features
include state-of-the-art technol-
ogy, extensive testing and relia-
bility. Tested and assembled, the
Dual-Stor comes complete with
disk controller board, DOS,
BASIC compiler, assembler,
string-oriented editor and debug
software. Suggested retail price is
$2300.

Vector Graphic, Inc., 31364
Via Colinas, Westlake Village
CA 91361.

One-Hand-Typing Keyboards

Computing is a simple, one-
handed task with the Writehander
keyboards. Available for either
right or left hand, these small new
keyboards provide characters for
computers, terminals, displays
and other 128-character ASCII-
or ISO-coded devices. The new
model features snap-action
switches, improved circuitry and
keypressed signals as well as
strobe pulses to signal that data is
available.

The Writehander keys are
mounted on a rugged five-inch

diameter hemisphere that con-
veniently accommodates the
human hand. The shape and key
locations have been designed so
that the fingers and thumb natu-
rally fall on the appropriate
switches.

The small keyboard is finding
wide application for touch typing
and data entry where a free hand
is needed, such as for telephone
orders, computer programming
and for astronomy and micro-
scope observations. Pencil notes
may be written with one hand
while typing data with the other.

The keyboard code is easily
learned by blind people and those
with a disabled hand. When con-
nected to portable equipment, the
Writehander allows inventory or
field survey data to be conve-
niently entered with one hand.

The Writehander can be inter-
faced with any computer, ter-
minal, printer or other device that
will accept parallel 7-bit code
signals and provide the nominal
power required.

NewO Company, 246 Walter
Hays Drive, Palo Alto CA 94303.

OSI Introduces
Single-Board Concept

Ohio Scientific has just
developed the world's first com-
plete computer system on a board
incorporating a standard com-
puter keyboard, fast microcom-
puter, video display interface
with graphics, audio cassette, 8K
BASIC-in-ROM, up to 8K of
RAM and power supply on a
single printed circuit board.

This single-board concept,
made possible by Ohio Scien-

Morrow's new 16K static memory board.

Microdasys' MD-690A CPU board.

tific's six proprietary custom LSI
circuits, drastically reduces the
parts count and complexity, as
well as the price, of personal com-
puters. The new single-board
concept will be used in OSI's
Super Board 2, which will be a
complete computer minus case
and power transformer, and in
the 600P, which is a fully pack-
aged personal computer system.

Projected prices are $225 to
$279 for the Super Board 2 and
$329 to $379 for the 600P. Both
models are in pilot production
now and will be available in the
fall of 1978.

Ohio Scientific, 1333 S.
Chillicothe Rd., Aurora OH
44202.

CP/M for Micropolis and
North Star

Now Micropolis and North
Star Disk users can join the soft-
ware bus. Without any hardware
changes, CP/M can be run with
all the features available to the
users of the two systems on stan-
dard floppy disks. These features
include dynamic allocation
of diskette storage, relocatability
of system in memory, intrinsic
commands to save, rename, erase
and display directories of files
and complementary context
editor, assembler and dynamic
debugging program.

The software package for either
Micropolis or North Star in-
cludes: CP/M (Version 1.4),
$145; Microsoft FORTRAN-80,
$400; Microsoft Disk Extended
BASIC, $300; CBASIC Com-
piler/Interpreter BASIC, $95;
MAC Macro Assembler, $100;
SID Symbolic Instruction Debug-
ger, $85; BASIC-E Compiler/
Interpreter BASIC, $30.

Lifeboat Associates, 164 West
83rd St., New York NY 10024.

SuperRam 16

George Morrow, designer of
the ECONORAM 4K static

memory, has introduced a new
16K static memory board for
S-100 microcomputer systems,
SuperRam 16.

SuperRam 16 is a complete kit
featuring four independently ad-
dressable and write-protectable
4K blocks. The design uses just
11 ICs to keep the board un-
crowded and trouble-free. The
board was designed to meet the
proposed IEEE Standard for the
S-100, ensuring full compatibili-
ty with all S-100 systems. All
signals are fully buffered, in-
cluding address and data lines.
Morrow's 16K static RAM retails
for $299.

Thinker Toys, 1201-10th St.,
Berkeley CA 94710.

S-100-Compatible 6802/09

Added features of the MD-
690A CPU board over the capa-
bility of the MD-690 include: 6809
compatibility, 10K PROM space
and RS-232 interface provision.
The new MD-690 A combines the
computing power and software
compatibility of the 6802 proces-
sor with the hardware compati-
bility and widespread support of
the S-100 bus. This processor has
internal 16-bit arithmetic, 8x8
multiplication, 18 addressing
modes (the 6800 has six) and five
times the throughput of the 6800
(making it three times faster than
a 4 MHz Z-80).

The MD-690A comes complete
with MONBUG, a IK PROM
monitor program which is soft-
ware compatible with the stan-
dard Motorola MIKBUG moni-
tor; however, it is designed to in-
terface with most memory-
mapped video and graphics cards
for ultrafast I/O. The board can
accommodate up to 1 OK of 2716
EPROM, which may be used for
8K BASIC or other firmware.

The processor card also fea-
tures an on-card 2400 baud Man-
chester cassette interface, inter-
rupt-driven keyboard input for
fast I/O and provision for an
RS-232 interface. It provides you
with 16 I/O ports and DMA ca-

pability; there is IK RAM. The
board is high quality, double-
sided, plated through, solder
masked and silk-screened.

The suggested retail price for
the S-100 bus/MC6802/09 CPU
board, complete with the 2400
baud cassette interface, IK moni-
tor and IK RAM, is $198 in kit
form, or $258 assembled and
tested. Complete documentation,
including assembly and trouble-
shooting instructions, and a com-
prehensive user's guide are
provided.

Microdasys, PO Box 36051,
Los Angeles CA 90036.

ECT Mainframes
and CPU Board

Electronic Control Tech-
nology's 10-slot Table Top Main-
frames are of sturdy construction
(similar to ECT's industrial
ECT-100 19-inch rack mount
card cages). The TT-10 Table
Top Mainframe consists of an in-
dustrial quality card cage; the
MB-10, an S-100 bus mother-
board with bus termination and
ground plane to reduce noise; a
full set of 10 connectors and
guides; a 15 A at 8 V, 1.5 A at
-I- 16 V and 1.5 A at - 16 V power
supply, which mounts inside the
card cage; a clear satin finished
front/bottom plate with a reset
switch and power indicator LED;
a whisper fan and a vented tex-
tured blue cover. Assembled, the
mainframe sells for $395; the kit

costs $325.

ECT also announces its 8080
CPU, an S-100 bus 8-bit pro-
cessor board based on the 8080A
microprocessor IC. The clock is
crystal controlled and digitally
generated for optimum system
performance. 74LS244 bus
drivers are utilized to provide low
power with higher drive capabil-
ity. M WRITE is generated on the
board and a switch-selectable
'JUMP' on Reset circuit is pro-
vided for use in systems without a
front panel. Low-profile sockets
are provided for all ICs. The
board has solder mask, silk-
screened legend and gold-over-
nickel plated fingers. Kit, $120;
assembled $175.

Electronic Control Technology,
763 Ramsey Ave., Hillside NJ
07205.

UMB Universal Printed Board

Looking for a truly universal
printed circuit board? Whether
you're a design engineer evaluat-
ing a new circuit or a representa-
tive of a company that manufac-
tures custom and specialty sys-
tems, the UMB Universal Printed
Board is for you.

Other universal boards do
not accommodate both analog
and digital components on one
board without time-consuming
wire-wrapping or other modifica-
tion . . . whether you're working
with microprocessors or other
dual in-line packages. UMB is a
practical solution to many
breadboarding and production
problems. Its unique, two-sided
interlacing foil pattern incor-
porates four independent power
planes, each one bused to all 264
pad positions.

This design allows you to use
both analog and digital compo-
nents on one board. For example,
in mixed analog/digital circuits,
one side of the board provides
zero and +5 volt distributions,
and the other side of the board
provides - 15 and + 15 volt dis-

8080 CPU board with "JUMP" on Reset.

BOOKS

ADDICTIVE

1: MICROPROCESSORS:

Chips to Systems

Rodnay Zaks, 416 pp, $9.95

A MOK)PROGRAMMED
APL IMPLEMENTATION

PROGRAMMING
MICROPROCESSORS

A complete, progressive, educational
introduction to all aspects of microprocessors,
and the assembly of a system: basic concepts,
internal operation, the chips, system intercon-
nect, programming, system development.

This book has been qualified as 'best text
ever written on microprocessors. '

C202: MICROCOMPUTER
PROGRAMMING:6502

Rodnay Zaks, 250 pp, $9.95

8 BITS

ICROPROCESSOR
SELF-STUDY COURSE

■ I

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SYBtX

INTRODUCTION TO
MICROPROCESSORS

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WARNING: Readers have Determined
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C200: AN INTRODUCTION TO
PERSONAL AND BUSINESS
COMPUTING

Rodnay Zaks, 250 pp, $6.95

A comprehensive introduction to personal
computers, for home or business use: the
hardware, the software, the peripherals, the
costs. BASIC. How to fail with a business
system. How to select a system. Will it be
sufficient? Which one to buy.
Now on cassettes: 3 hrs, ref SIO, $14.95

A step by step introduction to microcomputer
programming, using the 6502 microprocessor,
with a detailed analysis of all basic program-
ming techniques, from arithmetic to Input-
Output, including interrupts.
Also available: 6502 APPLICATIONS BOOK

C207:MICROPROCESSOR
INTERFACING TECHNIQUES

Alesea & R.Zaks, 416 pp, $9.95

How to interface a microprocessor to the
external world, including all common peripher-
als: dynamic memory, keyboard, LED, floppy
disk, CRT display, cassette.
Includes the standard busses: RS232, IEEE 488,
SIOO.

SELF-STUDY COURSES

Includes Book and Cassettes

INTRODUCTION

TO MICROPROCESSORS (2.5 hrs) ref. SI, $29.95
TO PROGRAMMING (2.5 hrs) ref. S2, $29.95
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Esmark's new video integrated
electronic tracking pen.

tributions. This arrangement pre-
sents low characteristic imped-
ances to the power supply system
and, for most applications, mini-
mizes crosstalk between the ana-
log and digital distributions.

Two aspects of the UMB make
it especially suitable for proto-
typing and evaluating micropro-
cessor or interface circuits: (1) the
grid of 792 holes available for
components are aligned on .100
inch centers in both X and Y axes,
(2) none of the component pads
are tied to any of the power
planes; power planes are bused
beside every pad position and re-
quire only short jumper wires to
make a connection. Dual in-line
packages as large as 66 pins may
be accommodated on the UMB,
and smaller dual in-line packages
may be positioned in a variety of
configurations to suit the require-
ment of a circuit or system.

The UMB's construction al-
lows soldered circuits to be
changed without destroying
plated pad areas. Hole diameters
are .043 inch, large enough for
almost any component, and all
holes are plated-through. Posi-
tions for board isolation capaci-
tors are provided near the power
entry points. The board measures
4.5x4.0 inches. Price is $15.15
each.

Midgard Electronics, 175 Cali-
fornia St., Newton MA 02158.

Vidiet-Stik

Vidiet-Stik, a light-pen com-
patible with virtually all mini/
microcomputer systems, has
recently been developed by Es-
mark, Inc., 501 Vi E. McKinley
Hwy., Mishawaka IN 46544.

Vidiet-Stik (video integrated
electronic tracking) can be used
for: keyboard substitution with
real-time redefinition of key posi-
tions; interactive games; educa-
tional drills for preschoolers;

TPC's Model 101 case.

menu selection; joystick substitu-
tion; electronic music keyboard
replacement. The package in-
cludes the assembled and tested
pen, complete computer interface
instructions, operating documen-
tation, as well as checkout and
game software listings.

Vidiet-Stik software is compat-
ible with all 8080- and Z-80-based
systems; it is easily adapted to all
other mini and microcomputer
systems. The pen's hardware in-
terface requires only three elec-
trical connections: + 5 V, ground
and a single TTL level signal to
any parallel input port. The pen's
control software is relocatable to
any address and occupies less
than IK of contiguous memory.
The Vidiet-Stik is available for
$39.95 (plus $1.50 for postage
and handling); allow 4-6 weeks
for delivery.

Enclosures for Home-Built
Microcomputers

Want to add the "profession-
al" touch to your home-built
computer? Now you can with the
new line of enclosures for home-
built microcomputers and ter-
minals from Technical Products
Co., PO Box 12983, Gainesville
FL 32604.

Constructed of molded fiber-
glass, the case measures 20 x 18 x
8 inches and can support a video
monitor or portable TV on top.
The keyboard area (20 x 6 inches)
can accommodate both a full-size
keyboard and a hex-pad (not in-
cluded with case).

The case is finished with tex-
tured polyester resin and is avail-
able in beige, white or black. Cut-
outs (not provided) are easily
made with an ordinary saber saw.
Cast-in brackets are provided for
mounting to a base. The price of
the case is $59.95. A matching
fiberglass clamshell-type base
(one inch deep) is available for
$12.95. Matching expansion
modules for peripheral devices
will be available in the near
future.

Two-Part Computer Music

"Americana Plus" music soft-
ware is now available for use with
the Model 6 and Model 68 Music
Boards, Newtech's S-100 bus and
SWTP-compatible Music
Boards. "Americana Plus" con-
tains more than a dozen pre-
coded tunes, ready to load and
run, including five American fa-
vorites arranged for two voices.
Each voice can have a different
sound quality, and two music
boards can be used for stereo.

The MD-1NS disk for the
North Stark Micro Disk system
and the MD-1SW disk for the
SWTP MiniFLEX Disk System
(both $19.95) also feature "Juke-
box," a user interactive BASIC
program that permits easy selec-
tion of any tune. The MC-1SW
cassette ($15.95) for the SWTP
AC-30 interface contains the
same tunes as the MD-1SW disk.
An audio demo cassette with the
above songs is also available.
Model 6 and Model 68 Music
Boards, assembled and tested,
are available for $59.95.

Newtech Computer Systems,
Inc., 230 Clinton Street,
Brooklyn NY 11201.

Software from Software
Industries

You can start and maintain
your own mailing list with a gen-

eral-purpose mailing label pro-
gram from Software Industries,
902 Pinecrest, Richardson TX
75080. Mailing List operations
include: Add, Delete, Search,
Sorted List, Modify and Sequen-
tial Printout.

You have the option of a
Remark Field up to 64 characters
long for any additional informa-
tion, which can then be used to
sort or retrieve information. You
can also set up and change default
printing formats controlling the
exact placement of up to five
labels across a page, whether or
not to print the Remark Field and
the placement of the zip code.

The program is designed to be
easily used without any prior
knowledge of computers. Writ-
ten in Disk BASIC for a Poly-
Morphic Systems 8810 or 8813, it
comes complete on diskette or as
a hard-copy list for $40.

Supersoft Software

Supersoft, PO Box 1628,
Champaign IL 61820, introduces
two new software packages for
North Star Disk. These packs are
part of Supersoft's line of
'LOAD AND GO' software.

The Investment Pack contains
many programs covering the full
range of investments, including
options analysis, bond analysis,
intrinsic value of stock (Molodov-
sky method), a complete port-
folio management system, as well
as a two part macro-analysis
system. Several programs are
disk interactive.

The Family Pack is Supersoft's
answer to the gap between hob-
byist software and the strictly
business programs. The Family
Pack is aimed at the home and is
full of programs that range from
family/home budget analysis to
full-fledged mail and phone lists,
as well as tutorials in math and
spelling and a simple method of
writing perfect letters.

The Investment Pack and
Family Pack are $25 each.

Newtech 's Model 68 Music Board.

Si's Mailing List program

For starters.

#^5-

•ft

"•//

COSMAC VIP, the completely
assembled, ready-to-operate RCA
Video Interface Processor, opens up a
whole new world of computer excitement. New
challenges in graphics, games and control
functions. Yet it's just $249.00.

Easy to buy. And easy to program, thanks to
its unique, easy-to-use interpretive language.
You get a complete how-to book including
programs for 20 games: fun, challenging, and
ready to load and record on your cassette.

Simple but powerful.

Built around an RCA COSMAC micropro-
cessor, the VIP is a complete computer system
that can grow with you. It has 2K of RAM, ex-
pandable on-board to 4K. Plus a ROM monitor,
audio tone output to a built-in speaker, power
supply, and 8-bit input and output ports for
control of relays, sensors, or other peripherals.

Soon RCA will offer
options for color graphics
nd 256 tone sound generation,
ftn optional auxiliary keyboard
win opemjf) an exciting world of two-player
games.

Take the first step now.

Check your local computer store or elec-
tronics distributor for the VIP. Or contact RCA
VIP Marketing, New Holland Avenue, Lancaster,
PA 17604. Phone (717) 291-5848.

'Suggested retail price. Does not include video monitor or cassette recorder.

The fun way
into computers.

In the first Kilobaud Legal/
Business Forum I speculated on
the possibility of federal regula-
tion of microcomputers. In a very
real sense, it is no longer specula-
tion. Congress is now considering
the enactment of a bill that would
regulate the use of microcomput-
ers with respect to automated
telephone solicitation. Of course,
the bill is not aimed specifically at
microcomputers, but rather at
the regulation of unsolicited tele-
phone calls. But remember it is
microprocessor technology that
has raised the problem.

Jon Roland of the Micro Mart,
1015 Navarro, San Antonio TX
78025, and I discussed this prob-
lem at a recent trade show. The
following article was written by
Jon and directly addresses the
problems of computer-generated
"junk phone calls.

*»

An increasing volume of un-
solicited telephone calls, some-
times made or assisted by small-
computer systems, has resulted in
a demand for federal regulation.
This article will discuss the ways
in which microcomputers may be
used in this application, the legis-
lation that has been proposed to
regulate it and the possible im-
pacts of such use and regulation.

Junk Phone Calls and Micros

Microcomputers are being
used now to select or generate
telephone numbers and to dial the
calls. In some applications, a hu-
man solicitor does the talking and
records the result. A computer
may then be used to process the
results of the calls and make ap-
propriate reports. In a few cases,
the call consists of a prerecorded
announcement, which may invite
the person being called to re-
spond by calling back or by re-
maining on the line after the an-
nouncement is complete for a hu-
man solicitor to receive the re-
sponse.

In the future, microcomputers

Kenneth S. Widelitz
Attorney -at-Law

might make possible the issuance
of specific, personalized synthe-
tic vocal announcements and the
handling of responses by touch-
tone or speech recognition, thus
totally eliminating the human
solicitor except perhaps for ex-
ceptional cases.

Telephone soliciting is cost-
effective only for certain kinds of
products, services and markets,
and depends for its effectiveness
on being able to obtain a call list
of especially good prospects. An
example of a common applica-
tion is the sale of newspaper and
magazine subscriptions to per-
sons who have recently moved
into the area. It is often more ef-
fective than direct mail or broad-
cast advertising because the caller
is in a position to take an order at
the moment, just after the an-
nouncement is delivered, when
the prospect is most likely to re-
spond favorably. This psycholog-
ical factor, combined with more
effective ways of obtaining good
lists and the increasing cost of
direct mail compared to tele-
phone costs, has made telephone
soliciting increasingly popular
with merchandisers. The micro-
computer makes possible the
reduction of the last remaining
major cost: the personnel.

Most persons don't mind an
occasional unsolicited call, but as
the method becomes more pop-
ular, the volume of calls has be-
come a source of irritation to
many people, especially those
calls using a prerecorded an-
nouncement. The result has been
increasing demands for regula-
tion of the activity.

Garbage In —
Garbage Out (Maybe)

The Telephone Privacy ("Junk
Cair) Act of 1978, S2193, by
Wendell Anderson (D., MN) and
Thomas J. Mclntyre (D., NH),
and HR9505 by Les Aspin (D.,
WI) constitute the legislation that
is under consideration, at this

writing, before the appropriate
Senate and House committees. It
would prohibit unsolicited calls
to persons who indicate they
don't wish to receive them.

Telephone companies would
be required to furnish a current
list of parties who do not wish to
receive unsolicited calls. They
would be prohibited from charg-
ing customers for being placed on
the list. The penalty for making
an unsolicited call to a number on
the list would be $1000 or 30 days
in jail. The FCC would provide
specific regulations for imple-
menting the statute. Most tele-
phone systems in the United
States would be covered.

Also under consideration is an
Omnibus Communications Act
of 1978, and it is likely that the
Junk Call Act would be incorpo-
rated into the Omnibus Act be-
fore being sent to the floor of
each house. Because of the long
lead time between the writing of
this article and its appearance in
print, readers need to contact
their representatives in Congress
for the current status of the bill
and it contents.

One difficulty with this pro-
posed act as presently written is
that it calls for the list to be of
"names and numbers" rather
than just numbers. This would re-
quire persons with nonpublished
numbers who wished not to re-
ceive unsolicited calls to reveal
their numbers to avoid them,
since automatic dialing devices
could be used to call nonpub-
lished numbers, either by calling
all numbers in sequence or by
random number calling, as used
for polling. If the bill provided
for only a list of numbers, with-
out names being revealed, and
prohibited unsolicited calls to all
nonpublished numbers, this dif-
ficulty might be avoided. An im-
pact of this on telephone solicita-
tion would be to effectively rule
out calls to new listings not yet
made available by the telephone
company.

One way to implement such a
list would have an asterisk placed
beside the name of each party in
the directory who wished not to
receive unsolicited calls. A prob-
lem with this is that directories
are usually published only once a
year.

As this article is prepared,
nothing in this proposed act or
any other before Congress ad-
dresses the mechanism by which
unsolicited calls might be made,
and nothing has yet been seriously
proposed to regulate the use of
automatic dialing or calling de-
vices as such. The number of such
devices presently available or in
use is still small, and they have

not been found useful for sequen-
tial dialing of all numbers, both
listed and unlisted, for most kinds
of merchandising.

The only major use so far for
automatic dialing that is not
restricted to published numbers
has been polling, for which num-
bers are selected at random. Such
dialing could, of course, be re-
stricted to published numbers if
microcomputer systems were used
to control it. At this time the feel-
ing on Capitol Hill is that to try to
regulate the equipment is a solu-
tion in search of a problem.

Another difficulty with the
proposed act is the definition of
"unsolicited." Most people might
have what they think is fairly
good idea of what kinds of calls
they might find objectionable,
but not all these ideas are the
same, and few of them are easy to
put into clear, unequivocal lan-
guage. Does a person solicit a call
if he circles a number on a reader
service card in a trade publica-
tion? Could a guy wind up in jail
for calling a girl for a date at her
parents' home when the parents
are on the list? Does a person who
initiates an inquiry and reveals his
telephone number implicitly soli-
cit a telephone reply? This prob-
lem of definition is the main rock
that may sink the proposed act.

Could the Act Affect the
Micro Industry

Neither the problem nor the
proposed regulation to solve it is
likely to have an adverse impact
on the microcomputer industry.
On the contrary, it offers an enor-
mous opportunity. Microcom-
puters are not yet extensively used
for telephone soliciting or polling.
Most automatic dialing devices
are not microcomputer-controlled
at this time. Any regulation of
unsolicited calls would create a
severe need for microcomputers
by telephone soliciting opera-
tions, most of which are not yet
aware of microcomputers or suf-
ficiently sophisticated to make
use of them . If the proposed act is
passed, they will become almost
essential to any such operation.
They will be required to reliably
check numbers against the list of
prohibited numbers to insure that
calls to those numbers are not
placed.

The proposed act, however, is
not a satisfactory solution to the
problem of privacy. It is likely to
create more problems than it
would solve. Many on Capitol
Hill understand this, and passage
of the bill, as written, during this
session is doubtful.

How It Might Work

The real solution to the prob-
lem is to make use of microcom-
puter technology to make avail-
able to telephone customers a
low-cost terminal (what other
people call "receivers") that
could screen calls. This would be
facilitated by having the number
of the originating terminal or the
name or access code of the caller
transmitted to the receiving ter-
minal, which could screen the call
by reference to a lookup table and
decide whether to accept or reject
the call. This could easily be done
now for local calls by use of a
microcomputer device attached
to an ordinary telephone receiver.

The answering device would
announce to the caller that for the
call to be put through, he would
have to supply the appropriate
access code, by dialing or touch-
tone, and if the proper code were
given, the telephone would ring
(or forward the call or take a
message). This would not work
for long-distance calls if long-
distance charges were to be
avoided for rejected calls, but the
reciever might not care about

saving the money of nonaccepted
callers.

Present telephone tariffs and
court decisions make it easy to
implement such a device for use
by telephone customers, and if
the cost can be made low enough,
it is likely that there might be a
great many customers for such an
addition to telephones, especially
if combined with other useful fea-
tures.

Unfortunately, at this point it
would be expensive to convert the
telephone system to the automatic
transmission of the number of the
originating terminal and an ac-
cess code to the receiving termi-
nal, but this is clearly a feature
that needs to be incorporated in
the future. Legislation might be

needed to encourage this and
other needed improvements in
the telephone network to make it
ready for the coming generation
of multipurpose terminals that
will replace the telephone receiver
and most office machines, as well
as provide stand-alone computing
power to everyone.

Another needed improvement
in the telephone system is conver-
sion to pulse-code modulation,

and the transmission of all signals
digitally. Analog transmission is
wasteful of channel capacity.
Low-cost PCM communication
service would make feasible such
needed amenities as electronic
mail and electronic funds trans-
fer, and lower the cost of terminal
equipment. The use of real-time
trapdoor coding would provide
every person with reliable, pri-
vate, secure communications of
every kind and usher in a new age
of communication, information
processing and societal manage-
ment. Wiretapping, even by the
telephone company, would be a
thing of the past, except to moni-
tor signal quality and prepare
bills, since the coding would be
under the control of the cus-
tomer-owned terminal.

A Look to the Future

At this time, the need to make
an orderly transition from the
present system of voice terminals
to high-bandwidth multipurpose
terminals is not well understood
on Capitol Hill or adequately an-
ticipated in the presently pro-

posed Omnibus Communications \
Act or related legislation that
would impact on this subject.
There is a need for those of us
who can anticipate the needs to
make constructive inputs to the
legislative process.

Some things need to be said
about the legislative process at
this point in our history. It is
being said on Capitol Hill that
"it's not as much fun up here
anymore. ' ' The Voice of the Peo-
ple is becoming increasingly stri-
dent, demanding, uncompromis-
ing, discourteous and noncon-
structive.

More than ever before, our
elected officials are facing prob-
lems that are not well understood
by anyone and for which there are
no easy solutions that anyone can
readily agree on. People are mak-
ing demands that are impossible
and not understanding why those
demands aren't being met in-
stantly. What we need now is less
heat and more light. The readers
of this magazine, as a group, tend
to be more patient and positive in
their dealing with complex prob-
lems, but need to do more to help
solve the problems of the world.

Judging from the response we
are getting to our programming
problems, readers are anxious to
put their computers into action.
This is especially gratifying be-
cause it indicates that there are
still people out there who like to
charge their mental "batteries"
by solving challenging problems.
We plan to keep up a steady flow
of new problems so long as you
stay interested. By the way, if you
know of a programming problem
that would be appropriate, send it
along and we will try to use it in a
future column.

Before presenting the results of
the April problem, we have a few
letters to put before the Forum.
We are occasionally called on to
defend the use of BASIC, espe-
cially by beginning programmers.
(See the April column, for in-
stance.)

Not Just for Beginners

Apparently in the eyes of one
reader we have not been strong
enough when stating our position.
Viron E. Payne, 200 Juniper Ave.,
Merritt FL 32952, writes:

"Now just wait one minute.
You guys did a fine job in the
April issue of defending BASIC
from the standpoint of the begin-
ner, but that is really condemning

BASIC

FORUM

by faint praise. You let pass D. A.
Harrod's remark that he uses a
FORTRAN with a Double Com-
plex Hyperbolic Tangent func-
tion without bothering to ask just
who needs such a function. I am a
semi-retired electronic engineer,
and I have never needed one. I
also spent my time programming
in an engineering environment
for several years, and now do
varied types of programming.

"I started programming on an
IBM 602A Electromechanical
Calculating Card Punch, plug-
board-programmed yet . . . then
to a 607 electronic machine
(would you believe vacuum tubes),
also plugboard-programmed.
During this time I programmed
on an IBM 650 in a symbolic
language called SOAP (Symbolic
Optimum Assembly Program).
Next came FORTRAN program-
ming on the IBM 7000 series, fol-
lowed by a few years' program -

John Arnold/Dick Whipple

ming an IBM 1620 in a symbolic
language, SPS, in FORTRAN
and in machine language. I also
used a FORTRAN dialect called
FORCOM.

"A few years out of program-
ming, I started using a time-
sharing system having two
Honeywell 6000 (old GE 635)
processors hooked together and
operating as one big computer. It
had FORTRAN, BASIC, CO-
BOL and a few other languages
available. When I got on the sys-
tem I received handbooks on the
various languages. That was my
first look at BASIC. After look-
ing it over, despite my former ex-
perience with FORTRAN, I saw
that I could program anything I
would ever need to do in BASIC,
and do it much more quickly, so I
made the switch. I did write a few
programs in the time-sharing ver-
sion of FORTRAN IV, but these
only served to convince me more

that BASIC was the language to
use.

"After two years on this sys-
tem I purchased an Altair 8800A
in kit form and let my 16-year old
son assemble it for me. I got 4K
of memory and 4K BASIC and
played with it long enough to con-
vince me that I had a real comput-
er, not a toy, and then got 24K
more of memory and both 8K and
12K BASIC, all Altair Version
3.2, paper tape. I used the
ASR-33 TTY I had used on Ful-
ton Data Systems' time-sharing
system. I am pleased with what I
have and would not put FOR-
TRAN in my machine if someone
gave it to me. My programs do
not use that DCHT function, but
neither are they trivial.

"Much of my computer's time
is spent predicting the future
course of the stock market . To do
this I make a Fourier analysis of
the past price action to determine
the cycles present in the data and
then project these into the future.
Each point in a prediction in-
volves the sum of 30 or more trig-
onometric functions, and the
delay between printing lines is
only about two seconds. If the
TTY had a one line buffer there
would be no delay at all. I also do
a lot of word handling, including
large alphabetic sorts. Using
my own improvement of the
Shell sort algorithm, these run

fairly rapidly.

"I can usually sit down and
write a new program and have it
running before I would be able to
write the FORMAT, EQUIVA-
LENCE and COMMON state-
ments of a FORTRAN program.
I must have hard copy from
formed letters, not a matrix, as
my output must be used as offset
masters after being reduced half
size. Therefore, I am stuck with
the TTY and am usually I/O
bound. Increased speed would
help me little, if at all.

"Incidentally, the Altair
BASIC is far more powerful than
that on the time-sharing system.
Of course, the system had a won-
derful operating system and un-
limited disk storage, which was
nice, but their BASIC was posi-
tively primitive compared to
Altair's. I use the 8K BASIC
almost exclusively to conserve
memory space, and find it far bet-
ter than that on Fulton Data Sys-
tems. I have also compared it to
various microprocessor BASICs
and found it superior.

"For example, North Star
BASIC would be unusable in my
word-processing work. Its sub-
scripted string table capability is a
farce. I must have multidimen-
sional string table capability
without wasting memory by
filling in short strings with blanks
to the length of the longest strings.
The built-in Mini-Max function is
of great help in automatically

selecting the proper scale values
for plots of future stock-market
movements. Truly, the software
is the computer, and Altair
BASIC makes a fine computer.

"This has been a long letter,
but I hope it has convinced you
boys that BASIC is not just for
beginners — if you have a good
BASIC. I recently read that a
large time-sharing system has
been set up in Japan, used jointly
by three of the largest universities.
The primary language on the sys-
tem is an expanded BASIC. I
have an idea that much of the op-
position to BASIC comes from
programmers who are afraid that
BASIC will make programmers
so common that their livelihood
will be in danger. Now let's see
you defend BASIC for what it
really is: a very good program-
ming language, simple enough
for beginners to play with, but
capable enough, in the hands of
an expert, to do anything any of
the other languages will do."

BASIC— Here to Stay

Mr. Payne is certainly a satis-
fied BASIC user. He represents
the group who somehow wind up
using (and liking) BASIC after
years of working with other lan-
guages. There are others, how-
ever, who "cut their teeth" on
BASIC and then move on to more

10 REM. . .SCRATCHPAD UTILITY SUBROUTINE FOR PTCO EXTENDED BASIC

20 REM. ..EXAMPLE

30 DIM A$(16) ,R$(14)

40 LET Ai="FNTER V2(l): ":GOSUB 1000:LET V2(1)=A

50 PRINT V2(1)=";V2(1)

60 END
1000 REM... THE SUBROUTINE

1010 PRINT A$; : INPUT"", R$:REM.. . ""SURPRE3SES ?
1020 REM. ..HIT CARRIAGE RETURN FCR ACCESS TC SCRATCHPAD:
1030 IF LEN(R$)=0 THEN 1080

1040 REM.. .CHECK FOR NUMERIC INPUT: (NOT FOOLPROOF)
1(250 LET A=ASC(R$)

1060 IF A=43 OR A=45 OR A=46 OF (A>47 AND A<58) THEN LET A=VAL (R$ ) :RETURN
1070 GOTO 1010

10G0 ST0P:REM...N0W IN DIRECT MODE

1090 REM... TO RESUME PROGRAM EXECUTION TYPE (1) "A=XXXXXXXX" CR
1100 REM. .. (2) "CONT" CR

1110 REM. . .(XJXXXXXXX MAT BE A NUMBER OR A NUMERIC EXPRESSION)
1120 RETURN
RUN

ENTER V2(l) : -.125
V2(l )=-.125

READY
RUN

ENTER V2(l):
STOP IN LINE 1080
PS I NT 4?/. 91
51 .648351

A=47/.91
CONT

V2(l )= 51.648351

READY
RUN

ENTER V2(l):

STOP IN LINE 1080

A=SQR(2)
CONT

V2(l )-l. 4142136

READY

Program 1.

exotic languages. A member of
this latter group is Joseph D.
Shapiro, 1654 Feuereisen Ave.,
Bohemia NY 11716. Consider
these comments of a "former"
BASIC user.

"First, I learned programming
in BASIC on a DEC PDP-10, but
if my colleagues caught me
writing a BASIC program now, I
might find myself institution-
alized.

"I want to take this opportu-
nity to make a few statements
about BASIC.

"Second, for bad program-
mers, BASIC provides an excel-
lent medium for writing kludges;
this is probably the root of the
dim outlook most professionals
have for BASIC. But more im-
portant, BASIC provides a
medium for bad programmers to
become good programmers, and
good programmers to write a
good code. Furthermore, it is
publications like Kilobaud, and
columns like yours, that give be-
ginners the incentive to try new,
challenging problems, leading to
better techniques. Keep up the
good work."

We think the arguments for
and against BASIC will rage for
years to come. In our opinion, the
wide acceptance of BASIC among
micro-users has made most of the
haggling back and forth rather
academic anyway. BASIC is here
to stay.

Special Function Keys Needed

We recently had occasion to
use a Wang minicomputer and
one of the new IBM 5110s. One
of the features of these systems
(and some other commercial units)
is a set of special function keys on
the keyboard. Generally, these
keys can be programmed to link
directly to a BASIC subroutine
resident in memory. When a key
is struck, branching occurs to the
subroutine where a special pro-
cessing task is performed. The
keys can even be used while sitting
in an INPUT statement of an-
other program. Thus, you can
make special calculations while
entering data. Bob Lurie, 8 Twig-
ley Rd., Morristown NJ 07960,
has missed this feature on the cur-
rent crop of micros. He writes:

"Does there exist a BASIC in-
terpreter or compiler that permits
the user to conveniently do
scratchpad calculations prior to
INPUTting a number during the
execution of a program, or that
permits entering a numeric ex-
pression (i.e., 3*SQR(2)) rather
than just a number? Even the
simplest of the now widely avail-

able programmable calculators
gives the user access to a so-called
scratchpad, and one of my most
serious gripes about all of the
BASICs I've seen is that they lack
this — to my way of thinking —
elementary and essential capabil-
ity. It just doesn't seem right that
one should require a pocket cal-
culator at his side when sitting
down in front of a $2000 com-
puter!

"The enclosed BASIC utility
program (Program 1) for scratch-
pad (direct-mode) access was
written in Processor Technology's
new extended BASIC (almost
16K long, and 15 months over-
due, but still without extended
precision or string arrays!). In the
program I am writing, I no longer
use the INPUT command at all
for numeric variables (except as it
appears in the subroutine in lines
1000-1120). All calls for user in-
put now follow the format of line
40.

"Pretty cumbersome, eh! There
ought to be a better way."

Perhaps some of our readers
can come up with an implementa-
tion of special function keys.
Send your suggestions to The
BASIC Forum.

Contest Results

Now, the results of the April
contest. We received more than
50 entries. Most were well docu-
mented and only three were totally
incorrect. The problem as stated
was to write a BASIC program
that will: (1) accept any list of in-
teger numbers of three digits or
less (maximum of 100 numbers);
then (2) print the entire list as en-
tered; then (3) reprint all elements
of the list that appear only once.

First, let us make some general
comments.

1. Although we limited the
problem to a maximum of 100
numbers, we did expect the pro-
gram to be general and not writ-
ten specifically for the 26 values
in the sample run.

2. While data entry could be
via an INPUT or READ-DATA
statements, we expected the full
list to be printed after data entry
was complete. This served to veri-
fy that correct numbers were
placed in the list.

3. In (3) above, there was a
slight ambiguity. We quote from
a letter by Dave Leestma:

"In (1) you refer to integer
numbers of three digits or less,
but in (3) you ask to reprint all
elements of the list. If numbers is
the requirement, then leading
zeros or embedded blanks will be
ignored in determining a dupli-

10 REM KILOBAUD PROBLEM: APRIL 1978

15 REM AUTHORS: NANCY SCHWARTZ AND CAROL ASCOLILLO

20 DIM N(100)

20 FOR J=l TO 100

40 READ N(J)

50 IF N(J)=9999 THEN 75

60 PRINT N(J)J

70 NEXT J

75 PRINT

76 PRINT

80 FOR K=l TO J-l
100 FOR L=l TO J-l
110 IF K=L THEN 140
120 IF N(K)=N(L) THEN 160
140 NEXT L
150 PRINT N(K);
160 NEXT K

900 DATA 6,-10,15,7,7,7,6.-8,7,2,150,-6,13,12,12,5,-5
910 DATA 19,18,19,18,19,105,421,31,5,9999
999 END
RUN

6 -10 15 7 7 7 6 -8 7 2 150 -6 13 12 12 5 -5 19 18 19
IS 19 105 421 31 5

-10 15 -8 2 150 -6 13 -5 105 421 31

Program 2.

10
15
20
30
40
50
200
210
220
230
240
250
260
270
280
300
310
320
330
340
350
360
370
380
900
910
999

REM KILOBAUD PROBLEM: APRIL 1978

REM AUTHORS: NANCT SCHWARTZ AND CAROL ASCOLILLO

DIM N(100)

GOSUB 200

GOSUB 300

GOTO 999

REM SUBROUTINE #1:READ AND PRINT DATA LIST

FOR J=l TO 100

READ N(J)

IF N(J)=9999 THEN 260

PRINT N(J);

NEXT J

RETURN

REM SUBROUTINE #2:PRINT NON-DUPLICATED NUMBERS

FOR K=l TO J-l

FOR L=l TO J-l

IF K=L THEN 350

IF N(K)=N(L) THEN 370

NEXT L

PRINT N(K);

NEXT K

RETURN

DATA 6,-10.15,7,7,7,6,-8,7,2,150,-6,13,12,12,5,-5

DATA 19,18,19.18,19,105,421 ,31,5,9999

END

Program 3.

cate. If elements is the require-
ment then items must be charac-
ter-by-character identical in
order to be duplicates."

Good point, Dave. We meant
numbers in both (1) and (3). If
elements were correct, it would
suggest the use of strings to store
the data. Some entries (including
Dave's) used this technique. See
Bob Lurie's letter below.

4. We were not specific enough
concerning how entrants should
give the size of their programs.
Several stated their program's
size in bytes of memory, which is
fine, but most did not. In the fu-
ture, we ask that program size be
specified in bytes (8 bit) and in-
clude memory used for variable
and string storage.

These points made, let's look
at a few solutions. The first is no
doubt the simplest and most con-
cise. It was submitted jointly by
Nancy Schwartz, 16 Morse Circle,
Northboro MA 01532, and Carol
Ascolillo, 14 Morse Circle,
Northboro MA 01532.

"Enclosed are two solutions to
the problem presented in the

April 1978 issue of Kilobaud.
These were developed on a 12K
Altair 8800 utilizing Mits 8K
BASIC. The solution is presented
in two different forms: (1) direct
approach using nested "For To
Loops" (Program 2); (2) struc-
tured programming (Program 3).
We hope this will satisfy your
publication needs."

All elements of array N are
compared to all other elements of
the same array. The PRINT state-
ment is skipped if a duplicate is
found (other than an element
compared with itself)- Note there
is some wasted effort in that each
pair of elements is compared
twice. Execution time could be
improved, but memory efficiency
is quite good.

Many entries were quite elabo-
rate, both in algorithm and docu-
mentation. Kenneth Graham's,
182 Briar wood Dr. East, Berkeley
Heights NJ 07922, was a repre-
sentative example.

"Attached is a solution (Pro-
gram 4) to your 'Casting Out
Duplicates' problem. It was run
on The Service Bureau Com-

pany's CALL/370 time-sharing
system.

"I have two comments on the
instructions: (1) They do not say
that the entire list cannot be
printed out before further proces-
sing, hence I assumed it was
merely a formality to verify the
list as entered. (2) They do not say
that the items that appear only
once must be printed in the order
in which they appear in the orig-
inal list entered.

"Thus I used a simple method
based on the basic logic of an ex-

change sort. However, instead of
testing for greater than or less
than, the program only sorts
equal items into adjacent posi-
tions at the top. If there is no ex-
change necessary, the i"" item
must be unique. By swapping the
matching items, all remaining
items in the list are potential can-
didates for being unique elements.
If the items were printed in the
order they appeared in the orig-
inal list, the program could

(continued on page 25)

IINTEGER OF MORE THAN 3 DIGITS ENDS LIST

ILIMIT TO FEWER THAN 100 ITEMS
IN IS NUMBER OF ITEMS

IENTIRE LIST PRINTED FIRST

100 DIM L(99)

110 N=l

120 INPUT L(N)

130 IF ABS(L(N))>999 THEN 160

140 N=N+1

150 IF N<100 THEN 120

160 N=N-1

170 PRINT"LIST:";

160 FOR 1=1 TO N

190 PRINT L(I);

200 NEXT I

210 PRINT

220 FRINT"0NLT ONCE:";

230 1=0

240 1=1+1

250 T=9999

260 IF I>N THEN 390

270 J=I

280 J=J*1

290 IF J>N THEN 360

300 IF L(J)Ol(I) THEN 280

310 T=L(J)

320 L(J)»L(I*1)

330 L(m) = T

340 1=1*1

350 GOTO 28e

360 IF 109999 THEN 240

37e PRINT L(I);

3e0 GOTO 240

390 END

RUN

76,-10,15,7,7,7,6,-8,7,2,150,-6,13

712,12,5,-5,19,18,19,18,19,105,421,31,5

79999

LIST 6 -10 15 7 7 7 6 -8 7 2 150 -6 13 12 12 5 -5 19 ie 19 18 19 105
421 31 £

CNLT ONCE: 15 -8 -10 2 150 -6 13 105 4 21 31 -5

Program 4.

IFIRST PCINTER IS ITEM TO CHECK FOR MATCH
IDUMMT ITEM

!SCAN LIST BELOW FIRST POINTER ■

IEND OF LIST?

!IF ITEMS DO NOT MATCH KEEP SCANNING

IPUT MATCHING ITEMS TOGETHER AT TOP

IMOVE FIRST POINTER DCWN CNE
1KEEP SCANNING TO GET ALL MATCHES
IDID WE SWAP ANT ITEMS
!IF NOT, PRINT ITEM APPEARING ONCE
ICONTINUE THROUGH LIST

100

110

120

14e

150

160

170

180

190

200

210

220

230

240

250

260

270

280

RUN

REM.

REM

DIM

LET

.*A PROGRAM THAT CASTS OUT ELEMENTS THAT ARE EUPLICATEE
.(USES MINIMUM MEMORY-RUNS FAST)
.REF: BASIC FORUM KILOBAUD 4/7e
.BY: ROBERT J. LURIE MORRISTOWN, NJ
.PTCO EXTENDED CASSETTE BASIC VER A

,THE CHANGE.. HOW CLEVER!

A$(501) ,E$(24)

S$=CHR(160) :REM.

A$ = S*
INPUT E$

IF LEN(E$)<>0 THEN LET A$=A$*S$+S$ :G0T0 110
PRINTtPRINT A$:PRINT
REM

REM. ..HERE'S THE ROUTINE
REM

LET P=l

IF P=LEN(A$) THEN PRINT A$:END
SEARCH S$,A$(P+2),P1
LET P1«P+P1+1
LET E$=A$(P,P1)
SEARCH E$,A$(P1),P2
IF P2=0 THEN LET P=P1:G0T0 ie0
SEARCH E$,A$(P),P2
IF P2=0 THEN 180
LET P2=P2+P-1

IF P2+LEN(E$)>LEN(A$) THEN LET A$=A$ ( 1 , P2 ) : GOTO
LET A$=A$(1,P2)+A$(P2+LEN(E$)):GCT0 240

240

7SUGAR

7AND

7SPICE

?AND

7EVERYTHING

7NICE

\SUGAR\AND\SPICE\AND\EVERTTHING\NICE\

\SUGAR\SPICE\EVERYTHING\NICE\

READY

Program 5.

151 BOOKS

Computer Design Development

— Principal Papers
Ed. by Earl E. Swart /lander. Jr.

Hayden Book Company, Inc.
Rochelle Park NJ, 1976, $13.95

Nowadays it is hard to imagine
anyone getting excited over the
prospects of building an "elec-
tronic computing instrument"
featuring 4000 words of storage,
one accumulator, one "shift
register" and fewer than 32 in-
structions. And yet these are the
basic specifications for the first
real electronic digital computer,
as proposed in a June 1946 paper
by Burks, Goldstine and von
Neumann.

Earl Swartzlander has per-
formed a valuable service for all
of us by collecting this and 18
other papers of great significance
in the history of the digital com-
puter into a single reference book.
He describes his book as a "text-
book," but it is also both valu-
able and interesting reading for
everyone from computer hobby-
ists to computer-science students.
The collected papers range from
the first description of the flip-
flop (Eccles & Jordan, 1919) to
the design of the cache memory
for the IBM 360 (Liptay, 1968).
Papers included in the book cover
hardware design, pure mathe-
matics and the mathematics of
digital machines.

Just casually browsing through
this collection will reveal how old
some of our "new" ideas really
are. That high-speed wonder of
the second half of the 70s, the bit-
slice processor, is described in a
1951 paper by M. V. Wilkes. We
are also amused by some of the
early terms: "storage organ" for
main memory, and "order tank"
for instruction register. It is also
amazing to realize just how far we
have come in 25 years, from the
time when a proposed memory
access time of 50 microseconds
produced the comment: "It does
not seem possible physically to
achieve such a capacity." Or
from the time when that 4000
word memory is described as
being ten times the capacity

needed to solve "most prob-
lems."

Computer Design Develop-
ment will probably be required
reading for computer-science
students, but it is also a gold mine
of amazement and amusement
for the amateur and/or hobbyist.

Ken Barbier
Borrego Springs CA

Microcomputer Problem Solving

Using PASCAL

Kenneth L. Bowles

Springer-Verlag

New York, 1977, $9.80

Dr. Bowies' PASCAL is a text-
book used in courses taught at the
University of California, San
Diego. As such, it contains a lot
of material specific to UCSD's
version of the language, and a lot
of material specific to the ter-
minals used on the campus. You
might well ask, then, of what
value is it to anyone not attending
those courses or having access to
those terminals.

Speaking for myself, I shelled
out the decabuck required in
order to evaluate the capabilities
of PASCAL, as it is now avail-
able for 8080/Z-80 based micro-
computers, and my system is al-
most big enough to accommodate
this higher-level language. I had
been assuming that the next move
up for my system would be from
BASIC to FORTRAN IV, which
is also now available for micros.

I had previously investigated
PL/M and rejected it for reasons
I can only describe as "emo-
tional." I simply don't like
PL/M, regardless of it's capabil-
ities. In order to touch all the
bases, I acquired the PASCAL
book to see if there is a slight
possibility that the language has
any future in microcomputing.
And does it ever!

This book is more than just a
textbook covering UCSD
PASCAL. It is worth its price as
an introduction to programming,
usable even without access to a
computer — or as a guide to pro-

gram structuring. As I used it, the
book is a useful tool in evaluating
the new language. It also consti-
tutes a source book for ideas to
incorporate into a graphics
package (not confined to
PASCAL).

Any user of a micro or a mini,
programming in any language
from assembler up, will find
much of value in this book. The
danger involved in reading it is
that the chances are great that the
reader will become hooked on
PASCAL — which is what one
would expect, since it is a new
language designed to overcome
the weak points of its predeces-
sors. But it is in the presentation
of the various topics that the dan-
ger really lies.

The reader is led so skillfully
into the statements of the prob-
lems, the analysis of the pro-
grams to solve them and the dis-
cussions of other possible
methods that the book takes on
the flavor of a good mystery
story. The reader is led into each
topic in such an intriguing man-
ner that he becomes personally
involved and can't put the book
down until he finds out how it all
comes out!

What does come out in the end
is the realization that PASCAL,
helped along by the skillful pre-
sentation in this text, will prob-
ably become the small-systems
language in the near future. Com-
puterists whose only joy is in
number crunching will undoubt-
edly scream out that no other
language can replace APL. And
they are right, for their uses. But
for the rest of us, who do ac-
counting, controlling, text editing
or what-have-you, Ken Bowles
presents a convincing argument
that PASCAL is the language we
must implement on our little
machines.

Ken Barbier
Borrego Springs CA

A History ofn (Pi), 3rd Ed,

Petr Beckmann

St. Martin's Press, New York

Paperback, 200 pages, $4.95

"The history of pi is a quaint
little mirror of the history of
man. It is the story of men like
Archimedes of Syracuse, whose
method of calculating pi defied
substantial improvement for 1900
years; and it is also the story of a
Cleveland businessman who pub-
lished a book in 1931 announcing
the grand discovery that pi was
exactly equal to 256/81. . . ."
Thus starts what can only be
called a wry and offbeat book.

Petr Beckmann is a firm be-
liever in the need for an under-
standing of science and math-
ematics and uses his examination
of the history of pi to reveal the
foibles of man — pointing out
where he can because of his per-
spective that whenever there has
been ignorance and mysticism
there has been tyranny over the
ignorant and mystified.

The order of the book is,
naturally enough, chronological:
The Dawn of Man, The Early
Greeks, Archimedes of Syracuse,
Dusk, Night, Awakening,
Newton, Euler. Perhaps the most
interesting chapter is the one on
Euler, whom Beckmann, with
some justification, considers the
greatest mathematician who ever
lived. One example given is the
problem that had baffled mathe-
maticians for centuries: What is
the sum of the infinite series

l/P + l/2 2 +l/3 2 +l/4 2 + ... ?

As formidable a mathematician
as Leibniz failed to sum it, along
with Jacques Bernoulli who could
only prove that it did converge to
something. Not only did Euler
find the solution — shown by
Beckmann — but it turned out to
be ttV6, thus giving a formula for
the calculation of pi as fallout!

The later chapters deal with the
sad attempts to square the circle,
and the digit-hunters who (thanks
to Euler's many formulas) calcu-
lated pi by hand to more decimal
places. Surprisingly, pi had been
calculated (correctly!) to 500
places by Richter in 1855.

All of the interesting little
goodies about pi you've only
heard about come next: the proofs
of the irrationality and transcen-
dence of pi, formulas for compu-
tation, Buffon's Problem (com-
puting pi with a matchstick and a
grid of lines) and a nearly success-
ful attempt by the Indiana State
Legislature in 1897 to introduce
"a bill for an act introducing a
new mathematical truth and
offered as a contribution to
education."

This amounted to some stu-
pendous goofs in plane geometry
by a Mr. Edwin J. Goodman,
M.D., who deduced among other
things (and kindly offered his
findings to the state) that pi = 16/
v^, which is about 9.2. Fortu-
nately, a Purdue mathematics
professor found out about the bill
and coached the legislators. The
bill was dropped. From this pre-
sumably stem the unconfirmed
myths that a state legislature once
tried to define pi = 3.0.

The final chapter outlines (too
briefly) the history of digital com-
puter computations of pi, which

(continued on page 25)

Trouble-
shooters'

How do you troubleshoot a
"dead" system? Sooner or later it
happens to all of us — the system
dies. What to do? In the last few
columns we've used this question
to explore some fundamentals of
troubleshooting, and last month
we looked at substitution as a
means of defining the problem.
This month we'll wrap up the
basics by going into the theory of
tracing trouble.

The basic principles of syner-
gistic synectics, boxing your
problem, binary search and wall
moving are still prerequisites for
any type of debugging. Defining
the problem is usually the tough
part, and fixing it is the easy part.

Think of It as a Brainteaser

Tracing a problem is usually
slower than substitution and
often requires more equipment
and expertise. Though often the
choice of the professional who
has both, tracing certainly isn't
limited to use by the "experts."

If you have a knack for brain-
teasers, puzzles and problem-
solving in general, then tracing
will probably be not only effec-
tive for you, it will also be fun. It
certainly yields a heartwarming
sense of accomplishment when
the challenge has been met. Some
people I know revel in such
challenges. Anyone who can
"psych" himself into looking at
his bugs (including a dead system)
as bTainteasers wi\\ not only find
success more quickly but also
learn more in the process.

If you'll look back over your
own experience, you'll probably
find that you learned more from
your problem-solving experiences
than you did from books or
teachers! Of course, it's a lot
easier to think of it as a game if
you're working on a friend's
problem and it's not your own
system that just bombed out.

COKXEK

Ralph Wells

— both work invisibly. If you
want to see where a machine gun
is aimed, you substitute a tracer
bullet every so often. This tracer
may not be much of a bullet, but
it shows you where the action is
—dramatically. The same prin-
ciple applies to your computer:
Substitute something to make the
invisible visible.

This basic principle applies to
both software and hardware
problems. Both can be solved
more easily if you have special
equipment; however ingenuity
and "stick-to-itiveness" can
usually compensate for equip-
ment deficiencies.

Moving Walls

Last month I went into the
principle of boxing in your prob-
lem with walls and then moving
the walls together to get a clear
definition of what is really wrong.
When tracing is combined with ex-
pertise or just good common
sense, it can usually solve baffling
problems faster than the substitu-
tion methods discussed last
month. Both methods can move
the walls, and a good trouble-
shooter has both bullets in his
breech. As with substitution,
tracing should be used to set up
walls or divide lines between
elements of the system that are
known to be good and those that
are bad or are questionable.

Tracer Bullets in Your
Ammunition

A microcomputer works much
faster than a machine-gun bullet

Take It from the Top

The most common way to ap-
proach something is to start at the
beginning; we've been doing it
since childhood. This method has
its merits, but the fastest way to
find out if the butler did it is to
read the last chapter first. Look-
ing at the answers in the back of
the book may be unethical, but it
solves arithmetic problems, and
the principles involved are the
basis for tracing techniques that
are not only ethical but potent
(more on these later).

If we choose the take-it-from-
the-top approach to computer
problem-solving, then we will

start at the beginning of the pro-
gram (if it's a software problem)
or at the input of power or signal
(if it's hardware). Let's take the
soft side first. After the program
is loaded, then hitting RUN or
GO will set the program going at
the first statement like a conduc-
tor's downbeat. It will then pro-
ceed as it's "written" until some-
thing goes awry.

Our job is to find out where
and why it goes awry. You often
have clues that tell you some ele-
ments of the program are
working, so you can set up some
walls of the box before you even
start. The next object is to close in
your walls on the problem in as
few steps as possible, using the
"game plans" and binary search
discussed last month.

An obvious method would be
to find some point about halfway
through the program and install
some indicator, such as a STOP,
END, SOFTWARE INTER-
RUPT, PRINT or JUMP TO
ALARM routine. If it didn't get
that far before it bombed, then
divide the problem in two and set
your traps at one-fourth of the
way through your program, then
at one-eighth and so on, until you
find something that works.

A Software Trace

The top-down approach is
usually best implemented by
using a TRACE program if it's
available. A TRACE program
allows you to run your program
the same way you wrote it — step
by step. It usually works directly
from machine language, decoding
each instruction and displaying it
as it is executed. In its higher
forms it displays not only the
mnemonic op codes, data and ad-
dress values, but also the contents
of the primary registers, and
status codes (decoded), the ASCII
equivalents of the accumulator
and the addresses of branches
and jumps.

A really good TRACE will
allow easy modification of all
registers and memory contents. It
will also indicate how many sub-
routines "deep" you are into the
program and give you the option
of single-stepping through a sub-
routine or allowing it to run nor-
mally. It should also allow you to
start at any point in the program
and to run at normal (or near nor-
mal) operating speeds until it
reaches a predetermined point at
which it reverts to single-step.

If you intend to do much
assembly-language program-
ming, then you should try to get a
trace for your system. I've been

using Ed Smith's DISASSEM- I
BLER/TRACE for 6800 devel-
opment and the built-in monitor
trace on my Apple for the 6502.
Once you've used a good TRACE
program you get spoiled, and it's
so hard to do without it that I
don't think I'd try doing a long
program for any system that
couldn't be traced.

One Step at a Time

My first personal computer
(Altair 8800) had a rudimentary
TRACE function by virtue of its
single-step capability and the
LEDs on the front panel. It was
expanded somewhat by the Imsai
8080 and KIM that followed, but
it was still only a single-step func-
tion with limited readouts. It was
not until I obtained the second
version of Smith's TRACE pro-
gram for my Sphere (from Pro-
gramma Associates) that this
technique for debugging became
virtually indispensable.

TRACE isn't anything new—
the COBOL used in our big Bur-
roughs 3500 has had a TRACE
function for years; however not
many personal computerists can
afford it.

Disassemble a Bug

If you've been working with a
BASIC interpreter, you've prob-
ably had no need to investigate
the TRACE or its first cousin, the
DISASSEMBLER. As soon as
you graduate into machine lan-
guage you'll feel the need —
acutely. All TRACE programs
have to include most of the func-
tions of a DISASSEMBLER, so
it's common practice to throw in
this valuable feature in the same
package.

As you would expect from its
name, the disassembler reverses
the process of the assembler that
converted the mnemonics of an
assembly language into the
almost unintelligible (for
humans) binary code (object
code) used by your computer. A
good disassembler will calculate
the relative addresses and give
you the absolute address. It goes
straight through your program
and gives you a listing (assuming
that you have a CRT or printer)
that should correspond very
closely to your original program.

Comparing this disassembled
listing with your assembly-lan-
guage program will show up bugs
due to errors made in the original
coding, as well as assembler er-
rors, save/load errors and hard-
ware errors. The most common

bugs a disassembler reveals in my
programs are the syntax errors I
make in encoding, in particular,
my tendency to mix up absolute
values and page 1 addresses,
especially in the extended in-
dexing modes of the 6502.

Using a disassembler is similar
to proofreading a script. It shows
up your unintentional errors, but
if you didn't know how to spell a
word in the first place, it won't
call it to your attention. If you
have a synergistic relationship
with a friend who is also writing
for a similar system, then he can
often detect your boo-boos from
a disassembler check, just as my
proofreader picks up my split in-
finitives in these columns. I make
so many errors in my first draft of
a program that a disassembly of it
will almost always show some of
them up. It's a fast check, and
unless you have a lot of warranted
confidence in your programming
skills, it can probably save you a
lot of debugging time.

Blazing a Trail

When our forefathers ventured
into the unknown wilderness they
left their marks behind on trees
and rocks to mark their trail. To-
day the unknowns are different,
but the principles behind marking
a trail are just as valid. I've
already mentioned the use of
PRINT statements. "Sprin-
kling" a BASIC program with
PRINTs is one of the easiest ways
of marking a microsecond trail
that's taken a fatal turn in less
than the blink of an eye. Even a
PRINT sometimes takes too long,
but storing the data in a safe area
in memory can still solve the
problem.

If you're working in machine
language, then tracing a program
is more difficult. Most of the
older high-level languages (such
as COBOL), which are intended
to run on big computers, have
some sort of trace facility that
gives you a printout of the path
your program has taken. It means
wading through yards of print-
outs, and you have to do a lot of
recompiles — but it works.

Theoretically, you can do the
same thing with a micro, so I tried
it. It works, but I can't recom-
mend it . . . maybe if you're
working with a high-speed assem-
bler and disk, but not for the
usual "home" system and not for
me; not yet anyway.

Divide and Conquer

There are times when none of

the methods I've mentioned are
really effective. At these times
you should consider "unbun-
dling." There is an old parable
which states that even though you
may not have the strength to
break a bundle of sticks, you can
unbundle it and break one stick at
a time. This is the technique I use
when developing the software for
large systems: Tackle one seg-
ment at a time, debug it, then
take on the one adjacent to it. For
shorter programs the top-down
(first-things-first) approach
determines the order of segments
considered, but for the long ones,
the most difficult segment is
usually tackled first.

When the tough bugs are
solved, the remaining problems
in the program are usually rather
well defined so that debugging by
segments becomes the fastest way
to success. The dividing lines be-
tween segments become the natu-
ral points to set up "wall movers"
in the final debugging phase.

use both the end-in and top-down
methods in order to box it in. It's
very much like digging a tunnel
under a river from both sides at
once— when they meet in the mid-
dle, the job's done.

To the Rear — March

The normal flow for both
hardware and software is to start
from an input and proceed to an
output— the "from-the-top" ap-
proach. I've described several
methods of using the normal in-
puts and setting up temporary
outputs to trace the trouble. This
is the natural way we've always
solved problems, but it's not
always the best.

What if we reverse the proce-
dure — start from the rear and
work forward? It works! Em-
ploying this method, we use the
designated outputs as designed
and put in "test" inputs using the
same principles of wall moving
that we used for the top-down ap-
proach. The difference is that we
start running our program in the
middle and see if it comes out as
expected. If not, we keep moving
our START-RUN point closer to
the output until it does come out.

This method is often very dif-
ficult to use because the data ac-
quired during the bypassed input
routines has to be "dummied up"
into the proper registers and
memory locations. This is where
a good disassembler really helps
when debugging object code. All
of the registers can be readily
altered on a step-by-step basis, to
get things started.

If you're using BASIC, it may
be necessary to use temporary
routines and subroutines to be
sure that every variable is cor-
rectly defined. If the problem is
occurring in the middle of the
program, then it's usually best to

Hardware Tracing

If a system is dead, then the
problem is usually hardware.
Troubleshooting it with tracing
techniques is fundamentally the
same as the software techniques
we've been discussing. The prin-
ciples are the same but instead of
using PRINT, END, STOP, SWI,
etc., as temporary software out-
put devices (indicators), we use
oscilloscopes, pulse probes,
DVMs, state analyzers, etc., to
see the results at various points
along the way. When working
from the output into the pro-
gram, we use waveform genera-
tors, oscillators, pulse generators,
pulse injectors, software pulse
train routines, etc., instead of the
RUN-starting-at-line-#xxx that
we used for software debugging.

Equipment/Knowledge Trade-off

In an earlier column (Kilobaud
No. 20, August 1978), I had a lot
to say about the reciprocal rela-
tionship between knowledge and
test equipment. The more knowl-
edge, intelligence and experience
you have (or your friends have),
the less test equipment is re-
quired, and vice versa. Of course,
the bug will be found faster if
there is plenty of both, but there
seldom is! A good field service-
man for, say, a Tektronics ter-
minal, can fix the terminal in less
time than can a college professor,
and with fewer tools.

Tools of the Trade

Signal tracing is an ancient art,
probably as old as the field of
electrical engineering itself. The
optical galvanometer became the
volt-Ohm-milliammeter and then
the digital voltmeter. The ac volt-
meter was augmented by the os-
cilloscope, the storage "scope"
and the spectrum analyzer. Digi-
tal electronics and the microcom-
puter have spawned a new breed
of test instruments. The pulse
probes, for instance, can tell
whether any probed point in the
computer is on, off, high-imped-
ance, high with negative pulses,
low with positive pulses or single
pulses (as short as 10 nanosec-
onds), all for less than $50.

In the future, we will probably
see more signature analyzers in
common use. This device does for
the microcomputer what the digi-
tal voltmeter does for the tele-
vision serviceman. By putting a
known test signal into the com-
puter, the signature analyzer can
generate a (nearly) unique single-
byte signature for key test points
throughout the computer. If this
corresponds with the value ob-
tained from a schematic or a
trustworthy circuit, then the
troubleshooter moves on to the
next point or uses the binary
search principle outlined for de-
bugging software.

At the present time, these
devices cost as much as a small
computer (too expensive for me),
but as the cost of servicing micros
goes up and the field of signature
analyzers becomes more competi-
tive, they may become the way to
service the mass-produced micros
of tomorrow.

Physician, Heal Thyself

Another new hardware trouble-
shooting trend of the future is to
use the computer to diagnose it-
self! The best example is the
ROM-based diagnostic capability
designed into my PET. It even
has an LED indicator built in.
The problem is that Commodore
won't tell me (or even some of
their dealers) what's in it or how
to use it, so I have to service it my-
self, the hard way. A real pain!
Personal animosity aside, it is a
commendable pioneering step in
the field of troubleshooting.

Another current example of
self-analysis is the Electronic Sys-
tems serial output board I use in
the Apple II. The baud rate is
controlled by a pot setting of a
555 (oscillator). As a Teletype
driver it was a miserable failure
because most Teletypes won't
work reliably with only 5 volts
driving the 20 mA loop (Teletype
Corp. recommends at least 25 V
and standard communication
practice uses 40 V to 60 V). We
had to redesign it to drive the
Teletype with the + 12 V and
- 12 V supplies.

Then came a pleasant surprise.
A software frequency-setting
program that worked like a dream
was included. You entered the
desired baud rate and your CRT
became a digital frequency meter!
It displayed the 555 adjustment
both digitally and graphically.
You could see it all happen as you
tweaked the pot, and when you

had it optimized it set off a graph-
ic celebration of victory! Seeing it
do its thing can't help but make
you wonder how far away we are
from being able to dump in a
cassette, load a disk or plug in
a ROM and have the computer
run a complete set of diagnostics
on itself.

My TRS-80 has the rudiments
of such a test in its appendix (my
first one flunked it and was ex-
changed). As service data is com-
piled, more effective diagnostic
programs can be written, but this
can only be done by an aggressive
manufacturer. With the current
sellers' market there is little in-
centive, but the potential is there,
and it could revolutionize the
whole field of microcomputer
troubleshooting.

If you can teach BASIC on an
Apple II using software and no
printed material, why not some
interactive diagnostics? Of
course, the fallacy occurs when
the system is really dead, but with
some printed material and a
friend (or cooperative computer

store personnel) with a similar
machine, I find it hard to imagine
any common fault that couldn't
be traced and diagnosed without
requiring an experienced trouble-
shooter and an expensive test lab.
In fact, as the systems become
more complex, this could become
the only practical method of ser-
vicing tomorrow's mass-produced
systems !

A Retrace

To sum up the discussion on
tracing trouble, I'd like to leave
you with the following thoughts.

• Hardware and software prob-
lems are debugged using the same
basic principles — only the means
for indicating a temporary output
or originating an input are differ-
ent.

• Follow a logical game plan for
moving walls to box in your bug.

• Treat your problem like a
brainteaser puzzle — there's no
substitute for common sense.

• Approach your problem from

both ends of the tunnel.

• Don't be afraid to try trouble-
shooting your own computer.
Even if you fail occasionally,
you'll have learned to think a lit-
tle better, and that's probably
one of the reasons you bought it
in the first place.

• Your most powerful problem-
solving asset is synergistic synec-
tics — make a lot of friends!

• Divide and conquer.

It Seemed Like a Good Idea —
at the Time

When this column was started
in the July 1978 issue of Kilo-
baud, the editor and I both felt
that there was a need "out there"
for a sort of "Dear Abby" column
on troubleshooting. We set up
some guidelines and proceeded to
fill up the two-month delay be-
tween writing and publication
with some of the fundamentals of
debugging the hardware and soft-
ware problems of microcomput-

ers. By that time we expected to
be deluged with problems sent in
by the 100,000 or so Kilobaud
readers. It didn't happen.

This will probably be the last
Troubleshooters' Corner column.
If special situations occur (as in
the case of the EDN article on
troubleshooting the Apple II) or
if there is some newsworthy de-
velopment in this area, Kilobaud
will keep you informed through
articles on the subject. If you
have some specific subject that
you believe merits a feature arti-
cle, write Wayne Green at Kilo-
baud about it. I am only one of
several authors he could assign to
fill a need.

Or better yet, if you have a
solution that can really benefit
others, write about it and send it
in! I've found that trying to help
others has been fun; you will,
too. I have been preparing several
feature articles on other subjects
involving my 16 microcomputers,
which may be appearing in Kilo-
baud — I hope you'll find them
interesting.

K B CLUB

CALENDAR

Panama City FL

The Panama City Computer
Society (PCCS) was one of the
first organizations listed in the
Club Calendar when we started
nearly a year ago. Secretary Steve
Vickers wrote this month to say
that membership has now grown
to 44, and the group was planning
a computer fair featuring 15 sys-
tems during the last week in Sep-
tember.

Meetings are held on the
second Monday of each month at
the Springfield Library, Spring-
field FL. Details on the club are
available from Steve by writing to
PCCS, PO Box 6079, Panama
City FL 32901.

Microcomputer
Investors Association

A sampling of articles in the
latest issue of The Microcom-
puter Invester includes "Com-
modities—Are They Really
Worth Analyzing," "Random-

Steve Fuller

ness and Predictability of Stock
Market Prices" and "Measuring
Your Stock's IQ." Six of the
journal's ten articles include
computer programs that imple-
ment their authors' applications.
The Association's annual dues
are $30, and each member must
submit one article per year for
publication. For a membership
application, send an SASE to
Jack Williams, The Microcom-
puter Investors Association, 2415
Ansdel Ct., Reston VA 22091.

Got a Poly Hyphen?

Here's a newsletter for Poly 88
owners who have chosen to use
another manufacturer's disk sys-
tem. Thorn Hogan announces the
formation of the Poly-Hyphen-
Disk Users Group (PhD.UG) to
provide disk interface and soft-
ware assistance.

The sum of $5 will get you ten
newsletters featuring reviews of
various disk drives and how to
hook them up to your Poly, plus

software information and help
with system bugs.

Write PhD.UG, 719 Anna Lee
Lane, Bloomington IL 47401.

Birmingham AL

The current slate of officers of
the Birmingham Microprocessor
Group lists Tom Bowen as presi-
dent. Others include William
Fleet, vice-president; Jeff Lyons,
secretary-treasurer; and Joe Cal-
laway, editor of the group's
monthly publication, "Print-
out." The club meets on the
fourth Sunday of each month (ex-
cept November and December) at

2 PM.

Annual membership dues are
$6 per family, and visitors are
welcome at meetings. If you'd
like to contribute articles or pro-
grams to "Printout", or would
like more information on the
club's activities, write BMG, PO
Box 8072, Birmingham AL
35218.

AIM 65 Users Group

Rockwell's computer-on-a-
board, AIM 65, will be the sub-
ject of a bimonthly newsletter to
begin in January. Articles are be-
ing solicited, and subscriptions
are available for $5 from Target,
c/o Donald Clem, RR#2, Spen-
cerville OH 45887.

Cleveland OH

The Cleveland Digital Group
meets on the third Sunday of each
month a 2 pm. For information
on the Group's activities write to
club secretary Louisa Jartz,
CDG, 8700 Harvard Ave., Cleve-
land OH 44105.

Nobody's Perfect

For all the frustrated KIM-1
folk who have been trying to
reach Jim Zuber, maybe his cor-
rect address and phone number
will help! If you'd like to partici-
pate in his new San Fernando
Valley area KIM-1 User's Group,
write Jim Zuber, 20224 Cohasset
#16, Canoga Park CA, or call
him at (213) 341-1610.

This column is available for
you to report on your club 's ac-
tivities such as regular meeting
schedules, special events or pro-
grams, swap meets or any en-
deavor that will be of interest to
your fellow hobbyists. If your
announcement contains timely
information, please send it at
least two months prior to the date
or dates mentioned in the an-
nouncement.

Kilobaud Club Calendar

c/o Steve Fuller
334 Sterling St. Unit A -3
West Boylston MA 01583

*R*T£%

The Water's Fine

This is rather belated response
to the April 1978 Publisher's Re-
marks— "Go off the Deep End,"
but I want to thank Wayne Green
for his excellent advice in that
column then.

As a result, I first narrowed my
immediate computer choices to a
KIM-1 or a Heath ET-3400 and
studied the architecture and in-
struction sets of the 6800 and the
6502. Both are comfortable with
hexadecimal data entry.

Then I investigated the external
expansion possibilities and dis-
covered companies that could
provide such. I finally opted for
the ET-3400 complete with
Heath's Microcomputer Course.
(I can usually learn more, faster,
by assembling a kit than by
circuit-tracing an assembled
product.) Besides, the ET-3400 is
aesthetically more pleasing to the
eye than the KIM-1.

Now that I'm halfway through
the course and approaching the
breadboarding expansion of
memory and I/O interfaces, I am
less confused and more interested
and understand the basics better
than over a year's worth of
reading various articles and
books was able to provide.

The point is that I would still be
reading, becoming more con-
fused and waiting for the next
state-of-the-art advancement had
I not heeded Wayne's advice to
"start small and get wet."
Thanks, Wayne!

John R. Dye
Olympia WA

Well Integrated Company

f order integrated circuits and
other circuit components quite
often from your advertisers. In
most all cases, I have been very
satisfied with each company. One
thing that always annoys me is
additional charges. Usually,
there's a minimum order charge,
postage, handling and insurance.
Then, if I call the order in, there's
the cost of the phone call. Oc-
casionally, the price of the order
has doubled by this time.

One of your advertisers, how-

ever, eliminates these extra
charges. I'd like to commend the
service I get from Integrated Cir-
cuits Unlimited in San Diego CA.
Their prices are very competitive
and I've never received a bad
component. They have no mini-
mum order charge and not only
pay postage and handling, but
also pay for the telephone call
with their toll-free number.

Shipping is fast. I called in an
order on August 2 and today,
August 4, received the order!
They also honor several charge
cards, which is another conve-
nience. I highly recommend the
company.

D. Keith Henson WB4BYH

Knoxville TN

Choo-Choo Change

The optical sensor of the article
"Two Hobbies: Model Railroad-
ing and Computing" (July 1978,
p. 26) can be greatly improved by
replacing the binary-coded wheel
with one that is Gray coded. The
problem with a binary-coded
wheel is that a change in position
is associated with several bits
changing states. This can result in
gross positioning errors when a
dividing line bisects a photocell.

The Gray code was devised for
precisely this problem. It has the

property that each transistor is
associated with a single bit chang-
ing states. An example of a Gray-
coded wheel is shown in the ac-
companying figure. An excellent
tutorial of the Gray code is in the
Mathematical Games column of
Scientific American, August
1972.

The problem with the Gray
code is that is must be converted
to binary. The following algo-
rithms perform the conversion.

Letb n ,b n _j, . . . bj be the bits
in an n-bit number.

Binary to Gray code algorithm:
fori: =2 ton do
//bj = 1 then b\_\\ =>bj_i;

Gray to binary code algorithm:
for i: = n down to n do
//bj = 1 then bj_j: =>bj_j;

These algorithms can be imple-
mented in simple loops consisting
of a test sign, an exclusive OR
and a circular shift. Anyone
should be able to realize them in
less than 10 instructions each.

Stuart W. Rowland
Mayfield Hts OH

A DIM Statement

Beware of recently manufac-
tured Radio Shack TRS-80
systems. We received a sample
last week with an apparent defect
in the video monitor. If you run
the sample programs on page 109
of the Level 1 user's manual you
can check your system.

On three separate systems
we've checked in the Boston area,
all have a significant horizontal
wavering in the display when the
pixels are all lighted (i.e., when
the program is completed). Also,
there is a noticeable change in

ooooo

'0000

brightness as the display fills line
after line.

Take it back before your war-
ranty expires.

Robert Bonner
Brighton MA

— o

2 °
o o

o
o

An Enlightening Reply

Some slight wavering in video
screens is not uncommon, but
becomes apparent when the
TRS-80 's graphics capability is
used to "white out" the entire
screen. A severe skewing to the
right after about half of the
screen is painted indicates that a
resistor in the monitor should be
replaced. Radio Shack will be
most happy to effect this repair
for anyone experiencing this con-
dition. Mr. Bonner should return
his monitors to his local Radio
Shack store for repair through
our nearest Repair Center.

Dimming of the display when
the screen is painted totally white
is normal with our monitor, and
quite common on monitors we
have tested that are manufac-
tured by other companies for
microcomputer use. If Mr. Bon-
ner feels the dimming on his is
unusual, he should ask that it be
checked by the Repair Center
also.

I feel certain that if Mr. Bonner
will give our repair organization
the opportunity to correct his
complaint, he will be more than
satisfied with the results and the
short repair time involved.

Ed Juge
Computer Products Manager

Radio Shack

For This Reader
The '80's the One

It is most annoying to read let-
ters to the editor like the one from
Dave Caulkins in the September
issue (p. 19). Similar letters
disparaging the TRS-80 have ap-
peared in other publications. Ac-
tually, in my opinion the TRS-80
is a best buy. Not the best com-
puter around, and not for
everyone; but for the large
number of hobbyists and others
who want the kinds of capabili-
ties the TRS-80 has, it provides
the most quality and capability
for the money. I don't think the
competition is even close.

First a word about those criti-
cal letters and, in some cases,
review articles on the TRS-80.
Maybe Radio Shack should have
held up introduction of their
machine until the Level 2 chip
was available, since most of the

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Master Charge

criticism relates to limitations of
Level 1 BASIC that do not exist
with Level 2 (e.g., low recorder
baud rate, lack of keyboard roll-
over and limited string handling).

Level 1 is not bad when com-
pared with other systems in its
price range. In fact, it is quite
good and can serve many needs
quite adequately. What makes
even Level 1 a best buy, however,
is that it can be upgraded to Level
2 for only $99. When this is done,
about $500 in value is added
since, at least in my opinion,
about $400 must be added to the
cost of a Level 2 TRS-80 to pur-
chase a system of equal quality
and capability from another
manufacturer.

My Level 2 TRS-80 with 16K
RAM cost $789. For that sum I
have: (1) Z-80 CPU. (2) Video in-
terface featuring 16 lines of 64
characters (software changeable
to 32 double-width characters per
line for special effects), graphics
and automatic scrolling. (3) 500-
baud cassette interface with file
name recognition and verify. (4)
Microsoft-written extended (12K)
BASIC in ROM that is the equiv-
alent of top-of-the-line BASICs
from other manufacturers. (5)
1 6K of RAM (about 1 5 !4 K is user
available; the rest is used by the
BASIC and for general house-
keeping). (6) Standard size and
configuration keyboard.

To my knowledge none of the
popular systems, kit or assem-
bled, with the possible exception
of PET, can match or exceed
these capabilities for $1200, let
alone the under-$800 cost of my
TRS-80. When price-comparing
with another system that requires
loading extended BASIC from
tape, be sure to add the additional
cost of 12K more RAM (for a total
of at least 27K user available) in
addition to the extra cost, if any,
of the BASIC.

The PET might make the $ 1 200
price reference with comparable
capabilities, but in my opinion it
does not match the Level 2
TRS-80 at the same price. For
$795 the PET buyer gets a good
(8K) BASIC in ROM, but not as
good as Level 2; only 8K of RAM
and a nonstandard keyboard that
even PET owners dislike. How-
ever, a monitor and cassette are
integrated into the one-piece unit
and included in the cost. These
are extra-cost items with the
TRS-80 (included in the "sys-
tem' ' cost, but the TRS-80 can be
purchased without them). So a
potential buyer must pay his
money and take his choice when
deliberating between these two
systems. For my money, I chose
what I consider to be the better
basic (and BASIC) machine and

purchased the recorder and a very
good surplus monitor separately
at a cost considerably lower than
if purchased from RS.

Concerning quality of the
TRS-80, 1 can only say my system
has operated flawlessly. Recorder
problems, common to most sys-
tems and the most frequently
read complaint about the TRS-
80, have been minimal and trace-
able either to operator error or
some "bargain" surplus tape I
purchased.

The best-buy status of the
TRS-80 can only be improved as
manufacturers of peripheral
equipment respond to the large
potential market of TRS-80
owners. Kilobaud and others are
predicting that soon, if not
already, there will be more
TRS-80s than all other makes
combined.

A parting word for Dave
Caulkins. I do agree with the last
sentence of his letter, although
my interpretation is undoubtedly
different from his. Indeed the
PET and TRS-80 are not of
equivalent quality.

Hal Brown
King of Prussia PA

TV or not TV

In the September 1978 issue (p.
18) Dr. Meyersfield inquired
about hooking a standard TV to a
TRS-80 system. This is the same
approach that I took, since the
output is a standard video signal.
I first attempted to use an rf
modulator, but had limited suc-
cess with it due to limited band-
width.

Next, with the help of a Sams
Photofact schematic of my set, I
tried a direct tie-in to the first
video amplifier and achieved a
readable picture. However, the
characters still ran together some-
what, so I extended the band-
width a little by removing the
sound IF traps. The final change
gave a display almost the quality
of the TRS-80 monitor. The
bandwidth required for the
TRS-80's 64-character line is
more than most unmodified sets
can handle.

Sets not to use for conversion
are color and small (diagonal of
nine inches or less) screen b&w
models. Also beware of the shock
hazard involved in using sets with
a line-connected chassis. I found
Don Lancaster's TV Typewriter
Cookbook (stocked by Radio
Shack) very helpful with the
process.

Robert A. Lacy
Schenectady NY

I read with interest Dr. Meyers-
field's letter in the September
1978 issue of Kilobaud because I
also saw no sense in paying an ad-
ditional $200 for a CRT monitor.
(I bought the Level 1 4K machine
only.) However, I was shocked
when I read the editors' reply.
You said parenthetically, "The
Radio Shack has an opto-isolator
built in so more than a simple TV
modulator is required."

What, then, is a Pixie- Verter? I
am successfully using an unmodi-
fied Pixier-Verter and 12-inch
b&w TV. The setup works great.
Naturally, it is not as good as
direct video, but for the 16 lines
of 64 characters and 48x128
graphics, it is sufficient. If there
is something special about a
Pixie-Verter, I would like to
know about it.

I have subscribed since Vol. I,
No. 1, and, except for this mat-
ter, have been satisfied with your
magazine.

Jerry Owen
Hopewell VA 23860

Marketable?

I am writing to inquire whether
you feel there is a market for a
computing service I am consider-
ing offering: the production of
high-quality output copy, suit-
able for offset printing, from
Tarbell coded audio tapes or
minifloppy disks. This idea has
come to me after observing the
unsuitability of most small-
computer output devices for
preparation of copy for printing.
The quality, for example, of pro-
grams reproduced in journals is
terrible.

I see two potential classes of
users for this service: publica-
tions (newsletters and magazines)
that use word-processing systems
for preparation of their text; soft-
ware publishers, who need to
print programs that would be im-
practical to retype.

Because the input would be
supplied by the customer, the cost
would be lower than regular type-
setting services, and the accuracy,
particulary in reproducing pro-
grams or object code, would be
improved.

I currently own the typesetting
equipment and am working on
the interface between it and a
microprocessor, and hope to
have it up and running by
September.

Daniel Eisenberg

1507 Sharon Rd.

Tallahassee FL 32303

Getting good copy on program

listings has been a bear in the
past. We've tried setting 'em in
type, but there seems to be almost
no way to get such a job done
without errors . . . or at least a
large waste of time. We 've been
working toward a solution to this
for Kilobaud (and Instant Soft-
ware) via a couple of the Micro
Term Selectric II systems. We
have these presently connected to
the TRS-80 and PET systems and
hope to have them I/O with most
of the other Kilobaud lab systems
soon. As far as providing a ser-
vice is concerned, you are up
against the same problem we are
with cassettes: a wide variety of
formats. I think you'll find that
not more than 10 percent of the
systems can yet use a Tarbell for-
mat, so you '11 either have to get
more formats covered or else
limit your business to that group.
I tried to stop this proliferation of
formats when I organized the
Kansas City meeting back in
1975. — Wayne.

National Computer Tournament
for the Prisoner's Dilemma

Looking for a challenging
project for your strategic in-
stincts and your programming
skills? This computer tourna-
ment may be for you. There is no
charge to enter.

The tournament is based on a
game called the Prisoner's Dilem-
ma. In the Prisoner's Dilemma
there are two players. Unlike
most games, such as chess, the
two players are not in total con-
flict. In fact, both can do well or
both can do poorly.

Here is how the tournament
works. The game will be played
for an average of 200 moves, and
in each move, each player can
choose either to cooperate or to
defect. If both cooperate, both
do well. But if one defects while
the other cooperates, the defect-
ing player gets his highest pay-
off, and the cooperating player
player gets taken for a sucker and
gets his lowest payoff. The catch
is that if both defect, both do
poorly.

The precise payoffs in the tour-
nament for a given move are 3
points each if both cooperate; 5
points to a player who defects
while the other cooperates, with
points to the sucker; and 1 point
each if both defect. The score of a
player in a single game is his or
her total over all the moves.

To win the tournament you
have to get the highest total score
summed over all the games you
play. Therefore your object is to
get a good score in each separate

game, but not necessarily to get a
better score than the player with
whom you are currently playing.

To join the computer tourna-
ment, you submit a program writ-
ten in BASIC or FORTRAN IV
which will be a decision rule for
the selection of the cooperative or
the defecting choice at each
move. The decision rule may be
based on the history of the game
so far. For example, a simple and
effective decision rule is tit for
tat: cooperate on the first move,
and then do exactly what the
other player did on the previous
move.

Quite sophisticated decision
rules can be written in as little as
25 lines. This tournament is part
of a research project to under-
stand the nature of skillful per-
formance in a two-sided environ-
ment that is partially cooperative
and partially competitive.

Each person who completes an
entry will receive a report de-
scribing the results of the tourna-
ment. The winner will receive a
handsome engraved trophy.

To get further details on the
tournament, write to Professor
Robert Axelrod, Institute of Pub-
lic Studies, University of Michi-
gan, 506 E. Liberty St., Ann
Arbor MI 48104.

Info Needed

I recently purchased a used
Singer model 4325 helical line
printer. It uses an HSP-30
printer. The unit seems to be in
good shape, but 1 am in need of
any information I can get as to
the electronics portion of the
unit. Any information would be
very much appreciated. Keep up
the good work on a great
magazine.

Eugene Tetzlaf f

305 Poplar St.

Onalaska Wl 54650

On the Mark

It's a tribute to your magazine
that people get upset if they don't
receive it on time since it's always
timely and absorbing! The photo-
coverage of the Faire (June, July
1978) was wonderful . . . not too
many pictures at all . . . almost
as much fun as being there.

So far your editorial mix has
been right on the mark; don't
change a line of it.

Ted Wolff
New York NY

f^ltOOKS

(from page 18)

as of 1973 had seen no betterment
of the 1967 computation by a
CDC 6600 to 500,000 places in 28
hours.

If you don't mind a little bit of
political commentary on man-
kind's inhumanity and foolish-
ness (the remarks are not unjusti-
fied), you'll find A History of Pi
a fascinating history of mathe-
matics, famous and infamous
men . . . and plenty of good
anecdotes. The book is very
readable. It is better if you know
a little algebra and plane geome-
try and better still if you have had
a smattering of trig and calculus.
Nevertheless, this is a fascinating
story by an author who has done
his homework and uses his pen
both as a sword and a torch .

John Martellaro

New Mexico

State University

BASIC

FORUM

(from page 1 7)

easily be modified to replace the
exchange with a shift that moves
the matching item to the top and
shifts all remaining items down
one position.

4 * Keep up the good work."

Sort techniques like the one
Kenneth used are more elegant
and less "brute force" but not
necessarily better from a memory
time standpoint. Bob Lurie sub-
mitted a string version that com-
pares elements charater-by-char-
acter as you will soon see.

"You were right about this
being a deceptively simple prob-
lem. I spent hours before I
worked out all the bugs! I find
that judicious use of commands
such as PRINT "LINE XX
X P = " ;P can be very helpful in
following program flow and
tracing the position of the
pointers. These statements can all
be eliminated later.

"The title I have given to the
program (Program 5) is intended
to suggest that it is a member of a

general family of programs. I in-
tend to incorporate a routine > =
2=1 in a larger program I am
now writing.

"I enjoy your column very
much. Computing is what com-
puters are all about. I hope that
when APL becomes more gen-
erally available — I'm studying it
now — you'll expand your column
to include it."

Finally, two additional points
of interest. Ronald Anderson,
3540 Sturbridge Ct., Ann Arbor
MI 48105, sent us an interesting
solution. He solved the problem
two ways using 6800 machine
language and BASIC. The results
shown in Table 1 clearly indicate
that we pay for ease of program-
ming in BASIC with memory in-
efficiency and greatly increased
execution time. Everett Rubel,
S.R. 90574, Fairbanks AK 99701,
sent us a one line solution —
written in APL! We couldn't help
but be impressed.

The large number of entries
precluded our giving details of
all, but we have provided in Table
2 a list of the entrants' names. We
are sorry more could not be
printed.

A New Problem

This month's programming
problem is a favorite. It is a real
classic that literally predates com-
puters by centuries. We know it
as Josephus' Problem. For back-
ground on the problem we turn to

Maurice Kraitchik in his Dover
book Mathematical Recreations.

According to legend, the fa-
mous Jewish historian Josephus
saved his own life by a carefully
conceived strategem. After the
Romans had captured Jotapat,
Josephus and 40 other Jews took
refuge in a cave. His companions
were resolved to die rather than
fall into the hands of their con-
querors. Josephus and and one
friend, not wishing to die yet not
daring to openly dissent, feigned
to agree. Josephus even proposed
an arrangement by which the
deaths might take place in an
orderly manner. The men were to
arrange themselves in a circle;
then every third man was to be
killed until but one was left, and
he had to commit suicide.
Josephus placed himself and his
friend that they alone survived,
then escaped.

Develop a BASIC program
that can be used to determine the
elimination order for the general
case of Josephus' Problem (i.e.,
set up for the elimination of each
m"" person in a circle of n per-
sons. Use the data given above as
a test. For n = 41 and m = 3,
Josephus and his friend should
occupy places 16 and 31. Be sure
to include (1) name of computer
and BASIC, (2) execution time
(exclude printout) and (3) total
bytes of memory used. Send cor-
respondence to:

The BASIC Forum

PO Box 7082

Tyler TX 75711.

Method

Bytes Used Run Time Programming Time

6800 machine code

900 few l's second 10 hours

SWTP BASIC

= 10,000 43 seconds 1/2 hour

(including BASIC)

Table 1. Ronald Anderson's solution to ' "Casting Out Duplicates. "

1 . Ronald Anderson

2. Sandy Aubin

3. Richard M. Bash/Helmut Zinn

(from Germany)

4. Craig Bradley

5. Kenneth Busch

6. Ross Cooling

7. Courtney Ellis

8. Clive Frazier

9. David Garson

10. Gary Gaugler

1 1 . Ken Graham

12. Peter Granzeau

13. Rodney V. Hamilton

14. Morton Harwood

15. Bob Healey

16. Joe Holliday

17. Ralph Iden

J8. Knute Johnson

19. Ann C. Johnston

20. John Jordan

21. Tony Kalar

22. Joe Kopsho

23. Daniel Kott

24. Richard Lambke

25. P. LaPlantc

26. Dave Leestma

27. Robert E. Lehman

28. Rand Lewis

29. Robert Luckey

30. Bob Lurie

31. John W. McGaw

32. Alan Mcllhenny

33. Robert A. Mclvor

34. Greg Maggs

35. Theodor Mahler

36. Jim Martens

37. Joseph W. Mintzer

38. Norton C. Richardson

39. Brian Riley

40. Everett Rubel

41. Joseph Schaffner

42. Marv E- Schwanbeck

43. Nancy Schwartz/Carol Ascolillo

44. Buck Selby

45. Joseph Shapiro

46. Paul A. Sisul

47. Robert R. Urschel

48. George O. Wright

49. Su-Ming Wu

Table 2. ' 'Casting Out Duplicates ' ' entrants.

David Koh, M.D.
Dept. of Cardiology RG20
University of Washington
Seattle WA 98195

Raster Scan Graphics

for the 6800

(Part 1: The Hardware)

Is there any end to the modifications— and additional capabilities— that can be added to
the TV Typewriter II? Probably not. To show you what we mean— here's a real eye-opener.

Shortly after building my
SWTP 6800 system I set
about adding graphics capa-
bility to it. My choices at the
time were analog vector graph-
ics or bit-mapped raster scan
graphics. I had seen several
6800 vector systems in opera-
tion and was impressed by the
results. I was also impressed
by the amount of processor
overhead needed to maintain
the display and the difficulty in
displaying solid white areas. In
addition, I did not own a large-
screen vector display device. I
did have a high-quality TV moni-
tor, however, that I used with a
CT-1024 TVT-II as my terminal.

For these reasons I chose to
implement raster scan graph-
ics. The following describes
how a high-quality graphics
system can be built around the
SWTP 6800 and TVT-II.

There were several require-
ments I had in mind when devel-
oping this graphics system.

1. High density. I wanted
single dots, not squares or
blocks, and enough density to
display curves in a reasonable
manner. This design uses 256
horizontal dots, which, I feel, is
a minimum for serious graphics
work.

2. Static display. I wanted the
system to have its own memory
so it would display whatever
was stored there, regardless of

what the MPU was doing. The
MPU would be free to perform
its own tasks without having to
constantly refresh the display.

3. Fast update. I was inter-
ested in animation and wanted
to be able to change the picture
as rapidly as possible. This dic-
tated a shared memory ap-
proach in which the MPU could
read or write graphics RAM
directly through the system
bus. Transmission of data
through a serial or even parallel
I/O port would not be fast
enough.

4. Memory conservation.
This would be a side benefit of
memory sharing. The graphics
RAM looks like any other RAM
to the processor and could be
used as such to store programs
or data when graphics was not
being used.

5. Straightforward design. I
wanted neither hard-to-find
parts nor critical adjustments
in the circuit.

6. Ease of construction.

7. Low cost.

I looked at what was avail-
able on the market. Then, as
now, there simply were no com-
mercially available high-density
graphics boards for the South-
west bus. The GT-6144 was just
too coarse for my needs. The
only alternative was to build my
own.

I saw a promising-looking

graphics system design pub-
lished by Thomas Buschbach
in late 1976. The only catch was
that it was designed for a
Digital Group 8080 system and
Digital Group video interface.
Even though my microproces-
sor chip, processor board, sys-
tem bus and video system were
all different, I decided to see if I
could duplicate the results.

What has evolved over the
months is a virtually rede-
signed circuit that has finally
satisfied my requirements. De-
signing, and especially debug-
ging, it has been a tremendous
educational experience for me.
I present this article with the
hope that some of the many
SWTP 6800/TVT-ll owners will
try their hand at it and discover
the exciting world of graphics.

The circuit is sufficiently
complex that I do not recom-
mend it as a beginner's first
project. Anyone who has built a
few IC projects from scratch
should have little trouble with
it. Since no critical adjust-
ments or alignment are needed,
it should work the first time if
constructed properly. As in all
large digital circuits, though,
Murphy's Law dictates that at
least one wiring error will be
made. An understanding of
how your computer and ter-
minal work, an oscilloscope
and common sense should see
you through, however.

Design Considerations

I decided to use signals from
the TVT-II to supply the timing
for my graphics system. This
has several advantages: It
reduces cost and complexity
and takes advantage of the
phase lock loop of the TVT-H's
timing chain. This synchronizes
the vertical and horizontal
sweep to multiples of the
power-line frequency. The re-
sult is a rock-steady display
free of the wavering that com-
monly occurs with crystal-
controlled clocks when the
power-line frequency is slightly
off. Using TVT-ll timing also
allows simultaneous display of
graphics and alphanumerics on
the same monitor.

Centering the graphics pic-
ture is also done by the TVT-II.
The dot counter reset and line
counter increment pulse is pro-
vided by a signal I call
LOCKOUT. Not only does it pro-
vide the proper one-per-line
pulse, but it also locks out the
dot clock until the TVT-II left
margin set monostable times
out. This means the same ad-
justments for TVT-II margin and
line lengths will also set those
for graphics.

There was one catch to using
the TVT-II dot clock. Each char-
acter in the TVT-II occupies a 7
x 10 matrix. Horizontally, there
are f We character dots and two

blank "undots" for spacing;
vertically, there are seven char-
acter lines and three blank
lines for spacing. Since there
are 16 lines of 32 characters,
that means there are 224 by 160
dots available. No matter how
you configure the graphics
RAM you end up wasting bits
trying to match this format. 224
is also an awkward number to
deal with when you're writing
machine-language graphics
software.

The solution was to modify
the TVT-II format from five dots
and two undots across to five
dots and three undots across
per character. The change in
circuitry amounted to moving
one IC pin from +5 to ground.
The new TVT-II format is virtual-
ly indistinguishable from the
old one and in no way affects
normal terminal operation. The
result is a 256 x 160 dot matrix
that requires 5124 bytes, exact-
ly 5K, to support.

My graphics RAM consists of
a modified Southwest 4K mem-
ory board. This approach elimi-
nated the chore of wiring up
some 40 1K RAM chips plus
support chips from scratch. In
addition, half of the necessary
buffers are already on this
board. Turning the 4K board in-
to a 5K board proved to be a
simple matter accomplished by
piggybacking eight additional
2102L1 RAM chips. The re-
mainder of the circuitry is on a

small auxiliary board.

For the purpose of the follow-
ing discussion we can think of
the graphics board as a rudi-
mentary processor. Its sole
function is to cycle through 5K
of memory converting parallel
data into a serial stream for the
video modulator. Since there is
another processor on the bus,
namely the 6800, capable of ac-
cessing the same block of
memory, there must be a way to
settle simultaneous access
conflicts. This system gives
precedence to the MPU.

The RAM chip address and
data lines are isolated from the
main system bus and are nor-
mally driven by graphics cir-
cuitry. When a valid address ap-
pears on the system bus that
the graphics board recognizes
as being in its range, then it is
allowed to pass through to the
RAM address lines. At the same
time, the graphics on-board ad-
dress generators are discon-
nected, effectively giving con-
trol of RAM to the MPU.

If this is a read operation,
then true data will become
available after the access time
of the memory passes. At the
appropriate instant, the data
are strobed onto the system
bus to be read into the MPU.
For a write operation the ad-
dress lines are set up by the
MPU, data are applied to the
RAM chips and the system
write pulse is allowed to reach

the RAM chips. At all other
times, we must keep each pro-
cessor oblivious of what the
other is doing. In particular, we
must make sure that the RAM
chips will never put any data on
the system bus unless the MPU
requests them to.

Similarly, the system write
pulse must never reach the
RAM chips unless the MPU has
control of their address lines.
Isolation is provided by Tri-
state buffers that are enabled
and disabled by on-board ad-
dress decode and control logic
circuitry. It turns out that we
can leave the RAM Data In lines
always enabled since write
operations will occur only dur-
ing MPU accesses.

The write pulse requires
special handling. The address
applied to the RAM chips must
remain stable immediately be-
fore, during and after the write
pulse occurs. There must not
be any overlap or we will write
into memory locations other
than what we expected. Re-
member that our control logic

has to decode the system bus
address first before allowing it
to pass onto the RAM chips. Be-
cause of this delay the address
and write pulse reach the RAM
chips simultaneously.

Trying to correct this was by
far the most difficult task in de-
signing this circuit. Simply
delaying the write pulse with a
few TTL gates in series resulted
in trailing edge overlap. Using a
one-shot multivibrator to gener-
ate the write pulse worked but
required critical RC filtering to
prevent false triggering on
noise.

I tried using a circuit similar
to the Motorola 2 phase non-
overlapping clock driver in the
6800 data manual. This seemed
to work for a while until I tried
running long memory diagnos-
tics. It seems that repeated
write cycles will warm up the
2102L1 memory chips by draw-
ing more current in this mode.
This lengthens certain access
times internal to the chip and
alters the write pulse require-
ments. There was no telling
how many TTL gates I'd have to
string together to get the right
delays.

In the end the best solution
turned out to be the easiest. I
simply gated the write pulse
with a Phase 2 clock, which
never overlaps an address. Even
though the resulting write pulse
is narrower by a factor of two, it
has caused no problems and
should not, unless very slow
memory is used.

The subject of sparkle comes
up whenever you deal with DMA
graphics. This occurs when the
MPU accesses the memory at
some location other than the
one that is currently being dis-
played. Whatever that first
location contains gets loaded
into the shift register and out-
put to the monitor. If it is not the
same as the second location

AI30

GIC 13 \j_

I3_ 74 3 7 f

SWTP BUS <

AI4[>

AI5d>-

vmaO-

GIC 12 Ve
7420 r~

Fig. 1. Alternate board select circuit for C000-D3FF.

TTL VIDEO

TO FIGURE 3

2I02L-I DATA OUT LINES \

TRI-STATED

— MPU
SWTP * 2 ENABLE

50-PIN BUS

AO C>

LINECOUNT
RESET,

R/W O

I
5

SIGNAL GROUND

VMA G>

♦ THESE CHIPS ARE PART OF THE STOCK MEMORY BOARD

Fig. 2. Graphics system logic diagram.

(as it very likely is not), then it
appears as a momentary glitch
on the screen. When frequent
accesses are made, this
sparkle resembles a snow-
storm and can be very objec-
tionable.

The usual solution is to stop
the MPU and allow it to run only
during horizontal and vertical
retrace. The 6800 cannot be
stopped in a suitable manner to
use this scheme. In addition, I
did not want to slow down the

MPU since I was interested in
exploring animation and 3-D.

My answer to the problem is
to load zeros into the shift reg-
ister during an MPU access.
This has the effect of forcing an
8 bit all-blank sparkle. This
black-on-white pattern is much
less noticeable than random
white-on-black sparkle and is
virtually invisible if a medium
persistence phosphor is used.
The screen does not blank out
during MPU accesses, and the

MPU runs at full speed using
this scheme.

High memory seemed to be a
logical place to put the graph-
ics RAM. Keeping it separated
from main memory protects it
from being clobbered by pro-
grams like BASIC that search
for the end of contiguous mem-
ory on initialization.

My system has 16K of main
memory at locations 0000 to
3FFF and 5K of graphics RAM
at 6000 to 73FF. A toggle switch

on the board moves graphics
RAM down to locations 4000-
53FF when I need 12K of con-
tiguous memory for word pro-
cessing, assembling large pro-
grams, running long BASIC pro-
grams and the like. For fully ex-
panded systems Fig. 1 shows
how to wire the board for C000
to D3FF, a region where there is
currently no conflict in the
SWTP 6800 MIKBUG system.

At present, this system does
not support color or intensity
modulation (Z or gray scale).
There is no reason why the
basic design cannot be expand-
ed to include these features,
but to do so requires more
memory, which would best be
done by employing higher den-
sity RAM chips.

How It Works

For this section and through-
out this article, the following
convention will be used for
numbering ICs: ICs that already
exist on the TVT-II board are
prefixed by TIC, followed by
their number as found in SWTP
documentation. Existing mem-
ory board ICs are labeled MIC
and similarly numbered. All
new chips are considered part
of the graphics system and are
labeled GIC.

Main system timing is de-
rived from the TVT-II dot clock
(see Fig. 2). GIC 5 and 6 are the
dot counters that count down
the dot clock. A LOCKOUT
pulse, which occurs once per
line, both resets the dot count-
ers and increments the line
counters GIC 7 and 8. The latter

are reset by the LINECNT
RESET pulse from the TVT-II.

These four counters form the
graphics address generator.
Their outputs drive the 13 RAM
address lines A0-A12 to cycle
continuously through the 5K of
memory in ascending binary se-
quence.

GIC 15C is a triple input
NAND gate connected to GIC 5
as a divide-by-8 strobe. Its out-
put is connected to the mode
control of shift registers GIC 3
and 4 and causes a new byte to
be parallel-loaded every eight
dot-clock cycles. The dot clock
is also connected to the shift
register clock inputs that shift
out the eight bits serially, least

SWTP

50 PIN BUS

-O DO

-O oo i

-O DO
-O DO

-O DO

-O DO
-O DO
-O DO

EXISTING CONNECTIONS FROM 8835'S
TO 2I02L-I PINS M AND 12 ARE
LEFT INTACT.

DATA OUT LINES
TO FIGURE 2

♦ 5

GIC 13
7437

GIC 17
7402

~E>

n^zy- 1

GIC 13
7437

-►TO PIN 3 2I02L-TS QUAD

I, 2 (MIC 7)
-►TO PIN 3 2I02L-I'S OUAD

3, 4, 5 (MIC 36)

MIC 24
7402

( c \mic

UJ 740

|l6 | ' |l4 1 1 3 | . |ll

l'O |9

47 A8 A9 CT DO DI

*i GND

2I02L-I

A6 At) R/W Al A2 A3

A4 AC

|, | 2 | 3 |4 | 5 |e

|7 |e

TO UNBUFFERED ADDRESS
PINS OF ALL 2I02L-TS

& h 6

TRI^STATED
R/W

<t>2

MPU

+ 5
6

AI0 All AI2

ENABLE

TRI-STATED ADDRESSES

MIC 23
74SI38

FROM FIGURE 2

significant bit first, to the TVT-II
video section. Note that GIC 5
is preset to binary 0100, instead
of actually cleared. This lines
up the graphics image exactly
with the TVT-II alphanumerics.

GIC 1 and 2 are eight AND
gates with each input con-
nected to a RAM chip Data Out
line. Data will not appear at
their outputs unless the other
inputs are held at a logic high.
The BLANK signal from the
TVT-II sets these inputs low,
forcing the shift registers to
load zeros. This produces the
black top, bottom and side
margins.

MPU accesses are latched in
flip-flop GIC 16, whose output
also forces blanks. GIC 16 is
not reset immediately at the
end of the MPU access. In-
stead, blanking continues until
the next shift register load
operation occurs. This arrange-
ment prevents false data from
being loaded should the time
from end of MPU access to
shift register load be less than
2102L1 access time. In this way
sparkle is further minimized.

MIC 18, 19 and 2 / 3 of GIC 11
form the SWTP bus address
buffers. GIC 9, 10 and Va of GIC
11 form the graphics address
buffers. Enabling of these Tri-
state buffers is controlled by
address decoder GIC 12 and In-

Fig. 3. Memory board details.

verter GIC 14A. S1 sets the
board address range.

With A13 not inverted, an
MPU access will occur for any
address that appears on the
system bus in the range 6000-
7FFF (though with 5K, 73FF is
the last alterable location). In-
verting A13 sets the range to
4000-5FFF (last location 53FF).
Fig. 1 shows how the memory
range can be set for other loca-
tions if desired.

In Fig. 3, GIC 17D produces
the RAM chip write pulse by
NORing Phase 2 and the sys-
tem write pulse. GIC 13 B and C
are merely high-current buffers
needed to drive 40 paralleled
2102L1 write pins.

MIC 24 B, C and D enable the
bus driver sections of MIC 20
and 21 (8835 data bus trans-
ceivers) during MPU read oper-
ations. MIC 23 is a 74S138 1 of 8
decoder that enables the ap-
propriate 1 K bank of RAM chips
according to address lines A10,
11 and 12. Note that these ad-
dress lines are not buffered on
the unmodified memory board
and have been buffered
through GIC 11.

Fig. 4 shows modifications
to the TVT-II. Pin 2 of TIC 24 is
disconnected from +5 V and
grounded to convert from seven
dots per character to eight.
BLANK and DOT CLOCK sig-

.15

13
12

TO PIN I3'S OF

8 ADDED 2I02L-I'S

"QUADRANT 5"

nals are derived using
gate sections on the

spare
TVT-II

board. The DOT CLOCK must

be inverted through TIC 15A for
proper operation. LOCKOUT
and LINECNT RESET are taken
directly from appropriate
points in the TVT-II circuit. GIC
18, which is added to the TVT-II,
allows graphics display, alpha-
numerics or both on the same
monitor. TIC 4A is used to
divide the TVT-II dot clock by 2
if the circuit has been modified
for 64-character-per-line
operation.

Construction

Most of the circuitry resides
on an auxiliary board that
mounts to the 4K memory
board. One chip is added to the
TVT-II. The actual construction
technique is left to the reader. I
would recommend wire-wrap-
ping, even though I didn't use
that technique. Leads should
be kept as short as possible,
and heavy gauge +5 and
ground buses should be used.
In addition, be sure to bypass
power and ground with a 100 uF

FROM FIGURE 2
TTL VIDE0C>

GIC IB
7400

SPDT
CENTER
OFF

^E>i

TVT
OBOTH
GRAPHICS

?'«

♦ 5

GIC 18
7400

GIC IB
7400

aiH

TO TIC 23
PIN 10 o-

(TVT VIDEO)

VIDEO SELECTOR

TIC 17
7409

'^CD

1 1

TIC 19
74I32

BLANK <D-

TIC 5. PIN 2
• TIC 5, PIN 5

TIC 15
7400

DOT CLOCK <0

-oTIC I I, PIN 6
OR

CIRCUIT
FOR
64 CHAR/LINE

TIC 15
7400

TIC 4
PIN 13

DOT
CLOCK

CLK«

TIC 4a
7474

— 91

,TIC II
PIN 6

TIC IB
PIN 4

7 DOT TO 8 DOT MODIFICATION

LOCKOUT

LINECOUNT
RESET

SIGNAL
GROUND'

TIC 18, PIN 4

TIC 12. PIN 13

♦ 5

TIC 24
7495

J I

Fig. 4. TVT-II mods.

1 SWTP 4K memory board

1 prototyping board and edge connector

1 7805 5 volt positive regulator and heat sink

8 2102L1 RAM.chips

4 74193 binary counters

3 8T97 or 74367 Tri-state buffers

1 7420

2 7400
1 7437
1 7402

1 7474 D flip-flop

2 7495 4-bit shift registers
2 74LS08
1 7410

1 SPDT toggle switch
1 SPDT center off toggle switch

Resistors: all 1k, V* watt 10 percent for pull-ups.

Capacitors: 1 100 uF 15 volt electrolytic and several .01 uF
disk ceramics for bypass.

Misc.: Ribbon cable, wrap-wire, IC sockets, 16-pin header,
Molex socket pins.

Table 1. Parts list.

GIC 5,6,7,8
GIC 9,10,11
GIC 12
GIC 14,18
GIC 13
GIC 17
GIC 16
GIC 3,4
GIC 1,2
GIC 15
S1
S2

electrolytic capacitor and sev-
eral .01 uF disk ceramics.

The prototype was built us-
ing a Radio Shack prototyping
board (276-152), IC sockets and
point-to-point wiring. The ICs
on the auxiliary board interdigi-
tate with those on the memory
board, and, consequently, the
whole assembly fits in a single
slot of the SWTP motherboard
(see Photos 1 and 2).

This is probably not possible
if wire-wrapping is used, unless
the socket pins are cut down. I
piggybacked several TTL chips

on top of existing memory
board chips to reduce the num-
ber of wires going onto and
coming off the auxiliary board.
If this does not suit some
readers, then there should be
enough room to squeeze these
chips onto the auxiliary board
with careful layout. Table 1 con-
tains a parts list for the modifi-
cation and Table 2 lists the IC
power pin-outs.

The first step is to verify that
all computer-system compo-
nents, including the TVT-II,
SWTP 6800 and the 4K memory

Photo 1. The completed auxiliary board mounted to the modified
4K memory board. Interconnections to the TVT-II are made by the
edge connector at the top of the auxiliary board. Note the eight
new 2102L1 RAM chips (marked with white squares) added to the
memory board and the new regulator and heat sink. A 16-pin DIP
header, which plugs into an IC socket piggybacked atop MIC 25,
provides an easy connection point to the ten low-order RAM ad-
dress lines.

GND

+ 5

74LS08

7495

7400

7410

7420

7402

7437

7474

74193

8T97

Table. 2. Pin-outs for IC power
connections.

board, are working. Be sure the
memory board is functioning
perfectly before attempting to
modify it. If you are construct-
ing any part of the system I
urge you to use sockets for all
ICs.

The following sections de-
scribe in detail the necessary
modifications and additions.
TVT-II

The TVT-II requires minimal
modification.

1. Convert from seven dots
per character to eight dots by
lifting pin 2 of TIC 24 from +5
and connecting to ground. This
is most easily done if the IC is
socketed. Pin 2 can be carefully
bent out straight and reinserted
in its socket. Connection to pin
2 is made by soldering directly
to it or to a Molex socket pin
which is slipped over the IC pin.
If the IC is soldered to the board
then you must cut the pin care-
fully near the board using a fine
tool. Readjust TVT-II R6 to
center the characters.

2. Locate pin 10 of TIC 23. On
the bottom side of the board a
trace leads from it to a plated
hole. Cut this trace carefully us-
ing a sharp blade. This breaks
the video path to TIC 17B pins
12 and 13.

3. Add GIC 18 (a 7400) to the
TVT board and wire it as shown
in Fig. 4 to form the video selec-
tor. S2 can be mounted up to
several feet away from the
board for convenient selection.
An easy way to mount the IC is
to glue it on its back to the bot-
tom of the PC board using a
cyanoacrylate glue such as
Super Glue. Connections can
be made by soldering directly
to the pins. Pin 1 of GIC 18 is the
TTL VIDEO INPUT line.

4. Wire the unused section of

TIC 19 as shown in Fig. 4. The
output of this gate is the
BLANK line.

5. Form the DOT CLOCK line
by inverting the TVT-II dot clock
through the unused section of
TIC 15. If you have converted
your terminal to 64 characters
per line then use the unused
section of TIC 4 to divide your
TVT-II dot clock by 2.

6. Locate TIC 18 pin 4. This
point will be the LOCKOUT
signal.

7. Locate TIC 12 pin 13. This
will be the LINECNTRESET sig-
nal. Incidentally, the Southwest
schematic shows this pin incor-
rectly connected to TIC 20 pin
13; it is actually connected to
TIC 13 pin 8.

8. Cut six lengths of insulat-
ed wire just long enough to
reach to the computer and
solder one to each of the five
signal lines we created in the
above steps and signal ground.
Do not omit the signal ground
even though your terminal may
be grounded through the power
line or RS-232 link.

Memory Board

Several modifications are
made to the 4K memory board.
The most visible is the addition
of eight RAM chips to produce
a 5K board. The board select
circuitry is also modified, and
several lines need to be isolat-
ed through Tri-state buffers.

1. 1 strongly suggest labeling
the bottom Molex edge connec-
tor of the memory board with
each pin's function to avoid
making errors.

2. Add an extra 7805 5 volt
regulator to supply the aux-
iliary board. Mount it with
another heat sink on top of the
memory board lower regulator
using a longer screw and metal
spacers to ensure metal-to-
metal contact 1or good hea\
transfer. Bend the input and
ground pins down and solder
them to the corresponding pins
of the lower regulator. Solder a
heavy flexible wire to the out-
put pin. The other end will be at-
tached to the 5 volt bus on the
auxiliary board.

3. Solder a heavy wire to
ground near the Molex edge
connector. The other end will
be attached to ground on the
auxiliary board.

4. Lift the following IC pins
either by bending them out and
reinserting the ICs in their
sockets or by cutting and bend-
ing if they are soldered in.

(a) MIC 18 pins 1 and 15

(b) MIC 19 pins 1 and 15

5. Three foil cuts are. neces-
sary, and a pull-up resistor
must be added.

(a) Trace the connection
from MIC 19 pin 7. Cut the
trace as it goes around C7
at the lower left corner of the
board on the component
side. Be sure to cut it before
it reaches any of the R/W
pins. Note that this trace
has a plated through hole
near pin 9 of MIC 35. Locate
the three plated through
holes in the + 5 line near pin
9 of MIC 36. Solder a 1k 1 /.
Watt resistor between these
two points.

(b) Cut the trace that goes
between MIC 19 pin 9 and
MIC 7 pin 3 on the compo-
nent side of the board.

6. Remove the board address
select jumper and tie point A to
ground by connecting it to MIC
23 pin 8. We have now by-
passed MIC 22, which can be
removed from its socket if you
wish.

7. Take eight new 2102L1S
and carefully bend each pin 13

straight out to the side. Piggy-
back these chips on top of MIC
26, 28, 30, 32, 34, 36, 38 and 40
(see Photo 1). Connect every
pin except pin 13 to the corre-
sponding pin of the chip below.
You can solder directly to the
chip or, better yet, solder a
16-pin socket to the lower chip
and plug in the piggyback chip
with pin 13 sticking out to the
side. Slip a Molex socket pin on
each pin 13 and tie all of these
together using fine insulated
wire. Connect the other end of
this wire to MIC 23 pin 11.

8. TakeGIC 11, 12, 13 and 14
and carefully bend every pin,
except power and ground,
straight out. Piggyback these
to the following chips.

GIC11 to MIC 19

GIC 12 to MIC 18

GIC 13 to MIC 20

GIC 14 to MIC 24
Form the leads slightly on GIC
12 and 13 so that the 14-pin
package will fit the 16-pin spac-
ing. Use a small hot iron to en-
sure a good solder joint.

9. Wire up the auxiliary
board. Don't forget to tie the
unused inputs on the counters
and flip-flops to +5 using 1k
pull-up resistors. Wire the con-
nections to the TVT-II to the
edge connector on the proto-
typing board. Wire up a mating
female connector with the
wires coming from the TVT-II.
Connect power and ground to
the auxiliary board. (Fig. 5 is a
component legend for Photo 2

Photo 2. The graphics board unmounted showing the ribbon
cables for address and data. The trimpot and empty socket remain
from previous versions and are omitted from the present design.
The single 256 mounting screw is visible just below the small can
capacitor to the right of the memory board.

—the auxiliary board and the
memory board.)

10. Wire the address decod-
er, write pulse, and transceiver
control circuitry. Connections
to the outstretched IC pins are
best made by hand wire-wrap.

11. Connect GIC 13 pin 8 to
MIC 7 pin 3 and GIC 13 pin 6 to
MIC 36 pin 3. This will supply
write pulses to all 40 RAM chips.

12. Use ribbon cable for the
address and data lines running
between auxiliary and memory
boards. A convenient way to
connect A0 to A9 is to piggy-
back onto any RAM chip using
a 16-pin socket and header.

13. Mount the auxiliary board
to the memory board using a 3 A
inch 2-56 bolt. This will require

J J J J

GIC II
8T97

IC 19 8T97

GIC 14
7400

| MIC 2 4 74

MIC 23

74SI38

EMPTY
SOCKET

MIC 21
8835

GIC 13
7437

JMIC 20 88

Fig. 5. Component layout for Photo 2.

drilling a 3/32 inch hole just
below and slightly to the right
of C1 when viewed from the bot-
tom side. Make sure that the
screw head will not contact any
traces.

14. Check and double-check
your work for wiring errors,
solder bridges, reversed ICs, etc.

System Checkout

With luck, your graphics sys-
tem should be functional. Plug
the assembly into the mother-
board, connect to the TVT-II,
set S1 for 6000-73FF, set S2 for
BOTH and power up. You
should see a pseudorandom
pattern of start-up garbage on
the screen. Switching S2
should display TVT-II, graphics
or both.

Using MIKBUG, enter 01 into
location 6000. This should put a
single dot in the upper left cor-
ner. Entering 80 into 73FF
should draw a single dot at the
lower right corner. Clear this
block of memory using a rou-
tine like ERASER (see Part 2 of
article) and repeat the above,
making sure that no other loca-
tions are altered.

If you've gotten this far, try
running some memory diagnos-
tics. This block should act like
any ordinary memory. If every-
thing works put away your
scope and start drawing pic-
tures. If you're having trouble,
the most likely fault is a wiring
error. Go back and check all
your connections again. If you
can't find anything, have a

friend check them too.

Listing all of the possible
fault modes would be impossi-
ble. Using common sense and a
scope to narrow the problem to
successively smaller portions
of the circuitry should locate
the problem, however. Check
power and ground for each IC
at its pins— not just at the
socket pin. Check that GIC 12 is
producing appropriate MPU
enable (active low) pulses dur-
ing MPU accesses and that the
two sets of buffers aren't en-
abled at the same time.

Scope the Tri-stated address
lines to check that the counters
and buffers are generating ad-
dresses. Check that data are
entering and leaving GIC 1 and
2 and are being shifted out of
the shift registers. If nothing is
getting out of GIC 1 and 2, then
look for problems in blanking or
blanking pulse generation. A
good TTL VIDEO signal, but
bad picture, implies a problem
in the video selector circuit.

Miscellaneous Notes

1. Keep the leads connecting

the TVT-II to the graphics board
as short as possible to mini-
mize noise pickup and radia-
tion. You may want to use
shielded cable for each signal
line. Do not use multiconductor
shielded cable as the tightly
bound wires will cross-couple.

2. The LINECNT RESET input
is the signal most susceptible
to noise. The reset pulse is less
than 100 nanoseconds wide
and occurs only once every 16
milliseconds. I inverted it going
onto the graphics board to
make it active low rather than
active high. TTL idling at a high
level rejects noise better than
at a low level. For stubborn
cases (evident as tearing and
jumping of the lower part of the
picture), try shielding this sig-
nal or adding a 1k pull-up
resistor to +5 on the graphics
board. As a last resort you may
want to try a line driver and
receiver pair such as the 1488/
1489 biased to - 12 volts. I have
had good results simply invert-
ing to active low.

3. If you run memory diagnos-
tics on this block of memory,

A hint of things to come . . . stay tuned.

remember one point— the addi-
tional RAM chips are ad-
dressed as quadrant 1 chips
(really quadrant 5), but are
physically mounted in quad-
rant 3 positions. Therefore, you
should use the quadrant 3 map
to track down bad bits in the
new chips. Refer to the table on
page 7 of the MP-M assembly
instructions.

4. Do not substitute a 7408
for the 74LS08 (GIC 1,2). These
gates are connected directly to

the 2102L1 Data Out lines,
which are guaranteed for only
one TTL load. Since they are
already driving that load (the
8835 driver inputs), an addi-
tional TTL load would exceed
the specs and result in a noisy
display. Low power Schottky,
being Vi of a standard TTL
load, works well, even though
the combined load technically
exceeds specs by several
hundred microamperes worst
case.B

Tired of trying to figure out how to make North Star BASIC do what you want?
Waiting to see if you can learn to program before buying a computer?
Need someone to "translate" the user's manuals for you?

Totally confused and frustrated?

The solution is -

The User's Guide

North Star BASIC

The essential book for anyone working with North Star BASIC.
Ask for it at your local computer store. Dealers contact:

inTERflCTWE

campuTERs

128

Interactive Computers
7620 Dashwood
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(713) 772-5257

Osborne & Associates announces two new books.

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World of the Brass Pounders:
Receive Morse Code the Easy Way

Microcomputing and amateur radio make an exciting combination, if you haven't already
discovered it. This Morse code reader is an excellent example of what we mean.

A great feature of a personal-
computing hobby is that it
can be used to work with other
hobbies. A case in point is this
little program to decode and
print out Morse code. I original-
ly wrote this in machine lan-
guage for my KIM system,
where it took up less than one

page, and finally decided to try
it in BASIC.

Even though the program
looks simple, it has some
unusual surprises, such as self-
adaptive adjustment for
changes in code speed. In addi-
tion, the influence of changes
in dash or dot length is weight-

ed so that they must occur five
or six times in succession be-
fore the computer decides that
there has been a bona fide
speed change. As a result, an
occasional "bad" character
will not mess up your copy; the
printout is extremely stable and
the copy is relatively foolproof.

1 REM MORSE CODE READER - WRITTEN BY R. KURTZ - W6PR0

2 RESTORE

3 PRINT CHR$(26):REM CAN DELETE - PUTS CURSOR AT TOP OF PAGE

5 DIM A$(100)

6 FOR N*l TO 100:READ A$(N):NEXT N

10 A=PEEK(5888) AND 1

11 IF A=l THEN 10
15 B =

20 A=PEEK(5888) AND 1:B=B+10

30 IF A*l THEN C» ( ( 5*C) + (2*B) ) /6 :D0=2*D0:DA«2*DA:D0»D0+1 :GOTO

40 IF B<(.5*C) THEN 20

50 D0»2*D0:DA=2*DA:DA*DA+1

60 A=PEEK(5888) AND 1:B=B+10

70 IF A»0 THEN GOTO 60

80 C*((4*C)+B)/5

100 B=0

110 A»PEEK(5888) AND 1

111 B-B+10

120 IF A»0 THEN GOTO 15

130 IF B<(.5*C) THEN GOTO 110

140 GOSUB 300

150 A»PEEK(5888) AND 1

151 B«B+10

160 IF A«0 THEN GOTO 15

170 IF B<(2*C) THEN GOTO 150

180 PRINT " "|

190 GOTO 10

300 DA=DA*2

310 D=DA+DO

330 IF D>100 THEN D=100

340 PRINT A$(D) ;

350 DA=0:DO=0

360 RETURN

400 DATA E,T,I,A,N,M,S,U,R,W,D,K,G,0,H,V,F,-,L,-,P,J,B,X,C

410 DATA Y,Z,Q,-, -,5,4,-, 3, -,-,-, 2, -,-,-,-,-,-, -,1,6,-,/,-

420 DATA -,-,-,-, 7, -,-,-, 8, -,9,0, -,-,-,-,-,-,-,-,-, -,-,-,?

4 30 DATA -,-,-,-,-,-,-,-,.,-,-,-,-,-,-,-,-, _,_,_,_,_,_,_,_

Program listing.

100

The program also detects the
end of the word and prints out a
space, if required.

The program's memory
needs are minor— just a little
over 1 K of RAM is required. The
program is written in Microsoft
BASIC on the KIM computer,
but should operate with any
relatively fast BASIC. From a
hardware standpoint, if your
CRT or printer will go to 300
baud, this program will provide
excellent copy of Morse code,
up to 15 or 20 words per minute.
If your terminal operates up to
1200 baud, it will follow the
Morse transmissions to well
over 30 words per minute.

Loading the Program

Input the program exactly as
written, even though some of
the instructions may seem re-
dundant. It is written this way
to save operating time— a very
important consideration when
you are dealing with fast-acting
dots and dashes.

Lines 10, 20, 60, 110 and 150
instruct a PEEK to location
5888 (decimal). In the KIM com-
puter, this is a peripheral input
address at 1700 (hex). This loca-
tion reads a total of eight input
ports as an eight-bit word.

The AND 1 on lines 10, 20, 60,
110 and 150 assures that the
computer is only reading the
port to which the incoming
Morse is connected. Obviously,

INITIALIZE

WAIT FOR
"KEY DOWN"

MEASURE
"KEY DOWN"

TIME

lE«
THAN

YES

Nj/2 DASH y^
J NO

STORE "DOT"
m DOT
REGISTER

STORE "DASH"
IN DASH
REGISTER

UPDATE
DASH-TIME

(WEIGHTED)

MEASURE
"KEY-UP"

TIME

PRINT
CHARACTER

PRINT
SPACE

Fig. 1. Simplified flow diagram.

this must be changed to fit your
particular system.

In addition, the program
assumes that when a dot or a
dash occurs, a logic appears
on the input port. This is in
agreement with a "key down"
shorting the input port to
ground, and also in agreement
with the hardware interface cir-
cuit described later. If your
hookup provides a logic 1 dur-
ing a dot and a dash, then lines
11, 30, 70, 120 and 160 must be
changed so that all IF A = 1
statements should read IF
A = 0, and vice versa.

Program Description

Fig. 1 is a simplified flow
diagram of the program. The
initialization routine (lines 1
through 6) sets the lookup table
that will permit the printout of
the proper character. The pro-
gram then waits for a key down
to occur (lines 10 and 11). The
first part of the operating pro-
gram (lines 20 through 80) mea-
sures the length of time that
the key is down and compares
this with the stored value for
the length of a dash.

If the key is raised in less
than one-half of the stored
dash time, the computer writes
a dot into the dot register (line
30) and goes to the second part
of the operating program.

If the key remains down
longer than one-half of the
dash time, a dash is stored in

the dash register (line 50), and
the value of the dash time is up-
dated with a one-to-four weight-
ing (line 80). This is accom-
plished by multiplying the old
value of the dash time by four,
adding the new value, and then
dividing by five. As a result, the
stored value of the dash time
cannot change drastically from
character to character, and the
copy is not susceptible to er-
rors from erratic sending habits.
The second part of the pro-
gram (lines 100 through 190)
measures the length of time the
key is up. If it's up less than
one-half of the dash length, the
program assumes that the
character is not complete and
no printout is provided (see
lines 100 through 130). If the
key is up longer, the program
jumps to line 300, the print-
character subroutine. If the key
is up longer than twice the dash
length, the program assumes
that a word is complete and a

EXAMPLE: D = — • •

Initial conditions: Dot register * 0, Dash register = 0.

First period: Input a dash.

2 times dash register =2x0 = 0.
2 times dot register =2x0 = 0.
Add 1 to dash register =1 +0 = 1.
Summary: dash register = 1, dot register = 0.

Second period: Input a dot.

2 times dash register =2x1 =2.
2 times dot register =2x0 = 0.
Add 1 to dot register =1+0 = 1.
Summary: dash register = 2, dot register = 1

Third period: Input a dot.

2 times dash register =2x2 = 4.
2 times dot register =2x1 =2.
Add 1 to dot register =1+2 = 3.
Summary: dash register = 4, dot register = 3.

End of Character— determine lookup number for D.

2 times dash register =2x4 = 8.

Add dot register and dash register =8 + 3 = 11.
Answer: D = 11.

Example 1.

1. If the input signal is a dash:

A. Double the values in the dot and dash registers.

B. Add 1 to the dash register (see line 50).

2. If the input signal is a dot:

A. Double the values in the dot and dash registers.

B. Add 1 to the dot register (see line 30).

3. If the character is complete:

A. Double the value in the dash register.

B. Add the dash and dot registers to obtain the lookup
number.

C. Clear the dot and dash registers.

Table 1.

"space" is printed (lines 170
and 180).

Lookup Table

The heart of the program is
the algorithm that counts the
dots and dashes and develops
a number used to look up the ac-
tual character to be printed. In
other words, each combination
of dots and dashes in Morse
code has a discrete number
that commands a given charac-

ter to be printed. This algorithm
has three conditions as listed
in Table 1.

Steps 1 and 2 keep repeating
until the character is complete.
When the program detects a
key-up period longer than one-
half of a dash length, it is as-
sumed that the character is
complete and step 3 is accom-
plished (fines 300 to 430). The
manner in which the lookup
number for the letter D is

♦ 9V

TO PA-0 ON KIM I

INPUT •— )\

K? "C

RELATIVE
RESPONSE

Fig. 2. Interface circuit.

Fig. 3. Circuit board.

formed is shown in Example 1.

Interface Hardware

Fig. 2 shows a typical circuit
for connecting your radio re-
ceiver to the computer. The
NPN transistor is an R/C
coupled audio amplifier con-
nected to a type 567 phase-lock
loop circuit. The free-running
frequency of the phase-lock
loop is set by the values of the

capacitor and resistor con-
nected to pins 5 and 6 of the
567, and is approximately 2000
Hz. The capacitors on pins 1
and 2 of the PLL adjust the
bandwidth to about 100 Hz, and
the LED serves as a tuning in-
dicator—that is, it will start
blinking when the signal is in
the center of this narrow band-
pass.
This circuit is compatible

with the program, as written, in
that the output signal goes to a
logic when a dot or a dash oc-
curs. The circuit shown is not
my original idea, but has ap-
peared in numerous publica-
tions; you may have your own
favorite circuit that you would
like to use. As long as you main-
tain the same output logic (a
for a dot or dash), there will be
no problem.

Incidentally, the circuit has
another unique application.
Since it is only activated by
audio signals over a fairly nar-
row band, it can also be used to
key an audio oscillator set to
any frequency desired. When
Morse CW comes in amidst a
jumble of other signals, the
phase-lock loop picks out the
signal you want and keys the
audio oscillator . . . and that is
all you hear. A full-scale outline
of the circuit board is shown in
Fig. 3.

Adjusting the Program

One of the advantages of

writing this program in BASIC
is the ease with which the com-
putation constants can be
changed. For instance, you
may wish to experiment with
different algorithms to detect
whether a key-down signal is a
a dot or a dash ... to take care
of "swing-fisters." This can be
accomplished easily by chang-
ing the factor in line 40 from
(.5*C) to (.25*C) or (.75*C). By
the same token, the constants
in lines 111 and 151 can be
changed to provide more lee-
way for the formation of char-
acters and spaces.

One final note for KIM users:
The 9K Microsoft BASIC is ex-
cellent and may be obtained
from Micro-ZCo., Box 2426, Roll-
ing Hills CA, for $100. In ad-
dition, a full kit of parts for the
interface circuit, circuit board,
Morse-code reader listings in
both BASIC and machine lan-
guage, and instructions on how
to connect it to an audio oscil-
lator are available from Micro-Z
Co. for $16.50 postpaid. ■

PET

■: n:i:±:t:*

, , StX*t« I I ||

X »JL« JL ****** JL *X* X «JL<

****« txtin

« MM*!

mm kmm ■■ mum mm

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[•«■

^ i

-_ iCHCSS*

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2 GI-F3
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nrcnnMR n

PLAY CHESS WITH YOUR COMPUTER!

MICROCHESS is the culmination of two years of chessplaying
program development by Peter Jennings, author of the famous 1K
byte chess program for the KIM-1 . MICROCHESS 2.0 for 8K PETs
and 16K APPLEs, in 6502 machine language, offers 8 levels of play
to suit everyone from the beginner learning chess to the serious
player. It examines positions as many as 6 moves ahead, and
includes a chess clock for tournament play. MICROCHESS 1.5 for

BRIDGE CHALLENGER by George Duisman for 8K PETs, Level II
16K TRS-80S, and 16K APPLEs: You and the dummy play 4 person
Contract Bridge against the computer. The program will deal hands
at random or according to your criterion for high card points. You
can review tricks, swap sides or replay hands when the cards are
known. No longer do you need 4 people to play! $14.95

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130

INPUT/OUTPUT UNLIMITED
13762 Victory Boulevard • Van Nuys, CA 91401

(213)997-7791

Parallel and Serial I/O Ports

This is the second session we'll devote to discussing computer input-output.

Peter A. Stark

PO Box 209

Mt. Kisco NY 10549

In the last session, we started
our look at computer input
and output by examining single
inputs and outputs, EIA levels
and current-loop interfaces.
This month we continue with
our discussion of parallel and
serial I/O ports.

The ASCII Code

Since popular personal com-
puters work on eight-bit bytes,

data can also go in groups of
eight lines. A group of eight
lines used for simultaneous in-
put is then called a parallel in-
put port; eight output lines are
called a parallel output port. Al-
though the eight bits can stand
for just some eight-bit binary
number, often they stand for a
coded alphanumeric character.
There are various ways to
code these characters, but the
most common and most popu-
lar is to use a code called ASCII,
the American Standard Code
for Information Interchange. In
this code, there is a specific bit

LEFTMOST 3 BITS

RIGHT-
MOST
FOUR
BITS

0000

000I

00I0

OOII

0I00

OIOI

OIIO

Oil I

I000

I00I

IOIO

IOI I

MOO

I IOI

IIIO

000
NUL

OOI
OLE

OIO
SP

I00

IOI
P

III
P

SOH

DCI

STX

DC2

ETX

DC3

EOT

0C4

ENQ

NAK

ACK

SYN

BEL

ETB

CAN

(

)

SUB

ESC

♦

•

1
1

—

DEL

Fig. 1. The ASCII code.

pattern for each letter, number
or punctuation mark. For in-
stance, the letter A has the pat-
tern 1000001; the number 5 has
the pattern 0110101; a space is
a 0100000. Although we could
make up a long conversion table
giving the codes and the char-
acters they stand for, most
often this is presented in the
compact form shown in Fig. 1.

Here we see the 128 possible
characters that can be made up
out of seven bits drawn in the
form of a table. For any given
character, we look up the first
three bits of its code at the top
of the table and the last four
bits at the left. For instance, for
the letter A we see that the left-
most three bits are 100, and the
rightmost four are 0001, so the
complete code is 1000001.

This table shows the ASCII
codes not only for the capital
letters, numbers and common
punctuation marks in the center
columns, but also for the lower-
case letters and a few other un-
usual punctuation marks at the
right, and some special control
characters at the left. These
control characters are abbrevi-
ated in the table— for instance,
NUL means null or empty, STX
means start of transmission,

LF is line feed, etc.

At this point you may have
noticed that we talked of eight-
bit characters, yet this table
only gives seven-bit codes.
ASCII is really only a seven-bit
code, but an eighth bit called a
parity bit is often added to it.
This added bit is used for detect-
ing errors in sending the char-
acter from one place \o another
and is often removed inside the
computer.

When parity is used, then for
any given character the parity
bit may be either a or a 1,
depending on what other bits
there are in the code. If even
parity is used, then each char-
acter code will always have an
even number of ones. That
means that if the seven-bit
code already has an even
number of ones in it, then the
parity bit will have to be a to
keep the number of ones even.

On the other hand, if the
seven-bit code has an odd num-
ber of ones, then the parity bit
will be a one, so that the total
number of ones will be even. (In
odd parity, the opposite would
be true.) As an example* the
seven-bit code for the letter A is
1000001. With the parity bit at
the left, in even parity the com-

plete eight-bit character would
be 01000001, while in odd parity
the complete code would be
11000001.

In many computer systems
the parity bit is not used, but a
full eight bits are still used for
each character. In that case,
the parity bit will always be the
same (a or a 1) regardless of
whether the total number of
ones is odd or even.

A good place to see ASCII
coding is in punched paper tape.
Fig. 2 shows a short piece of
tape. To guide the tape through
a tape reader and to provide
timing marks so the tape will
move at a constant speed, it
has a row of small holes
punched the entire length of
the tape. These are called
sprocket holes, just like those
on camera film. As shown in the
figure, there is space for five
other rows of holes to the left of
the sprocket holes, and three to
the right. A character is
punched as a set of holes going
across the tape. Each group of
holes going across the tape is
called a frame.

If you look at the sample tape
in Fig. 2, you will see that every
frame has an even number of
holes— either 2, 4 or 6. Thus
this tape was prepared with
even parity.

If you observe the notes on
Fig. 2 and read from top to bot-
tom, you can actually read the
punches on the tape by refer-
ring to the ASCII code in Fig. 1.
Hint: at the bottom, just before
the CR (carriage return) and LF
(line feed) is the date 02/11/77.

Experiment #63
Parallel Port Handshaking

Problem: Suppose an eight-
bit parallel port is used to send
a character from a computer to
a printer. How does the printer
know when a new character is
coming, and how does the com-
puter know whether the printer
has received it?

Solution: This is done with a
few additional lines for hand-
shaking. Actually, handshak-
ing is usually needed for both
input and output.

Theory : Fig. 3 shows the
overall block diagram of how
the computer might connect to
an output device such as a

Sprocket
holes

Rightmost

bit

Read this
way

Fig. 2. Punched paper tape in
ASCII.

printer. At the top we have the
eight parallel data lines, which
carry the ASCII character
(though sometimes it might be
only seven or even six lines)
coming from the computer's
output port. In addition to these
data lines, we show three more
lines, called handshaking lines.

When the computer has a
character to send out, it puts it
on the data lines and then
sends out a DATA READY sig-
nal to the printer. This informs
the printer that there is a char-
acter waiting. If the printer has
some sort of a holding register
(a group of flip-flops) that will
hold the character until it can
be printed, then the computer
will simply hold the character
there for some specified
amount of time before remov-
ing it.

But if for some reason the
output device is slow, then it
might be better if the computer
keeps sending out the character
until some signal comes back
saying that the character has
been accepted. This is the func-
tion for the DATA ACCEPTED
line.

Once the printer has the
character, it can start printing
it. This is usually a slow opera-

tion, and the computer should
not send out the next character
until the printer has finished
the present one. In other words,
the printer should send back a
READY signal when it's ready
for more data.

As shown in Fig. 3, we have
three handshaking lines. Some-
times we can make do with just
two (one each way), and other
times we may need more. But
this gives a good example of a
basic setup.

Procedure: For this experi-
ment, we will try a handshaking
circuit that might be used with
a reader for paper tape.

Most professional tape
readers have some kind of
motor or ratchet arrangement
for moving the tape. This com-
plicates the system, so let's
just talk about one of the sim-
ple readers that needs a human
hand to pull the tape through.

As shown in Fig. 2, punched
paper tape has room for nine
holes across the tape— eight
data holes and one sprocket
hole. So we need a way of
reading the nine holes. We
could probably come up with
some mechanical way of read-
ing them— metal fingers pok-
ing through the holes or a
toothed wheel riding over them
or something equally extrava-
gant—or simply try a photo-
detector sensing the light
shining through the holes.
Since we've already experi-
mented with a photo-transistor,
that seems like a good way to
go.

The holes in the tape are
spaced about 0.1 inch apart, so
we need a photo-transistor
small enough that nine of them
can be stacked in a row, with
0.1 inch spacing between them.
This is difficult to do, but fortu-

nately several manufacturers
make photo-detector arrays in-
tended for this purpose. There
are nine detectors in one
package, spaced the right
distance apart. So that's no
problem. (Remember— this is a
computer course, not a paper-
tape reader course. So let's not
go into too much detail here.)

Fig. 4 shows how we might
build such a simple tape
reader. Starting with a photo-
transistor array, we connect
each of the nine transistors to a
pull-up resistor to +5 volts and
also to some device that will
convert a slowly varying output
voltage into a nice square
pulse. A 7413 Schmitt trigger is
a good choice, since this is a
type of NAND gate that has a
very sharp switching point in
the output as the input slowly
varies. (The zigzag symbol in-
side the NAND means Schmitt.
If you don't remember them,
review Experiment #42 on
Schmitt triggers.) Another
possibility is a 555 timer con-
nected as a Schmitt.

When a photo-transistor is
dark (no hole), its resistance is
high, and so the Schmitt trigger
gets a positive input voltage.
Since the 7413 inverts, the out-
put will be nearO volts, or adigit
0. But when there is a hole, the
output will be positive, or a digit
1.

Of the nine photo-transistors,
the top five and the bottom
three provide the eight data bits
to the input port. But the fourth
from the bottom senses the
sprocket hole and has to be
treated differently.

The output of the sprocket
Schmitt trigger is sent to the
clock pulse input on a flip-flop.
The 7474 is a good choice here,
since it will trigger when a hole

COMPUTER

I/O

INTERFACE

PARALLEL OATA (8 BITS)

DATA READY

DATA ACCEPTED

READY FOR MORE DATA

OUTPUT

DEVICE

(FOR EXAMPLE,

A PRINTER)

Fig. 3. Typical handshaking for an output device.

is sensed, and the 7413 output
goes high. Since the D input of
the flip-flop is connected to +5
volts, the 7474 will set each
time a sprocket hole is sensed.

As you remember, the
sprocket holes are smaller than
the data holes. Therefore, the
data holes will arrive at the
photo-transistor first, and the
eight data bits will already be
present by the time the sprocket
hole is sensed. So the reader
first generates the data and
then sets the 7474.

The Q output of the 7474 is
sent to the computer as a DATA
READY signal. When the com-
puter senses the DATA READY,
it reads the incoming data from
the input port and then sends
back a DATA ACCEPTED signal,
which resets the flip-flop. As
shown in Fig. 4, this would have
to be a low signal to reset the
flip-flop, but by adding an invert-
er in the reader we could use a
high signal instead. In any
case, as soon as the data is
read by the computer, it sends
back a DATA ACCEPTED, which
clears the flip-flop and turns off
the DATA READY. This is im-
portant, because if the DATA
READY signal stayed on, the
computer might think it was a
new character and read in the
same character several times.

As you can suspect, with
proper handshaking, parallel
data transmission can be fast.
Characters can be sent as fast
as they can be generated or
received. Parallel data trans-
mission is always used with
fast I/O equipment, such as
disks, fast line printers, multi-
track computer tapes and so
on. But to go at its maximum
speed, parallel data needs at
least two handshaking lines in
addition to the data lines, for a
total of eight lines.

Experiment #64
Asynchronous ASCII Data

Problem: If you don't need
the speed, can you send eight-
bit ASCII data on fewer lines to
save some money?

Solution: Obviously yes, or
else we wouldn't have brought
it up. Instead of parallel data,
we send it in serial form. That
is, we send the eight bits on one
wire, but only one bit at a time.

Theory: If we send the bits
separately but on one line, then
the receiver at the destination
has to know which bit is which.
We could do this by setting up
several handshaking lines to
tell the receiver when the group
of eight bits starts and when it
ends. But this somehow seems
to defeat the whole pur-
pose—we are trying, after all,
to cut down the total number of

Let's define some of the
words used to describe this
kind of serial transmission.
Since the characters can arrive
at random times, they are not
synchronized with any clock
pulses. Hence this is called
asynchronous data; some-
times it is also called "start-
stop telegraphy" because it
dates back to the days when
teleprinters first started to

♦ 5V

74 1 3
TL

c
c
c
c

V EI6HT DATA BITS TO
' INPUT PORT

♦ 5V

7474

DATA
READY

PHOTOTRANSISTOR
ARRAY

ACCEPTED

Fig. 4. Logic diagram of a simple paper-tape reader.

lines.

So we put all this additional
information on the same data
line as will carry the data bits.
This is done by agreeing on a
very carefully timed sequence
as shown in Fig. 5.

First, we agree that the char-
acters to be sent may come
together in bunches or may be
separated by unknown and ran-
dom intervals of time. But once
a character starts, its timing
will be precisely controlled,
with each bit lasting a known
length of time. Since the
characters can arrive at unpre-
dictable times, we need to
decide what will be on the line
between them. As shown in Fig.
5, this is a 1 level, which lasts
up until the very beginning of
the character.

replace hand-sent Morse code.

Just before Morse code
started to be phased out in
land-based telegraph service,
they tried to record the Morse
code on paper tape by letting a
pen make a mark when current
was flowing through the wire
during a dot or dash. Between
the marks there was a space,
produced when there was no
current in the telegraph wire. In
modern current-loop teleprinter
circuits a current flow is a 1,
and an absence of current is a
0; but the old words mark and
space have still persisted, and
so we often call the 1 a mark
and the a space. In other
words, between characters
there is a steady mark level (a 1)
on the line.

At the beginning of a new

character, the signal suddenly

changes to a space (0) to form

the start pulse shown in Fig. 5.

Starting with this pulse, we

have a string of either 10 or 11

bits, which follow at a precise

speed. This consists of the

start bit, eight data bits, which

carry the ASCII character and

its parity bit, and either one or

two stop bits.

As you can see in Fig. 5, the

start bit is always a or space,
the eight data bits can be either
or 1, depending on the char-
acter code, and the stop bit is
always a 1 or mark. If the char-
acter is immediately followed
by another one, then the next
start bit will be right after the
end of the stop. If not, then the
stop will simply be continued at
a 1 (mark) level until the next
character comes along.

Fig. 5 also shows that the
bits are sent backward. For in-
stance, the code for the letter E
is 1000101. Assuming odd pari-
ty, the parity bit would be a 0,
and so the complete eight-bit
code would be 01000101. But
when sent over an asyn-
chronous line, the bits would be
sent backward as 10100010 as
shown. The reason is that it is
convenient if the parity bit is
sent last, so that it can be
checked after the rest of the
bits are received.

The bit timing has to be very
precise once the start bit starts.
Standard speed for a typical
model 33 Teletype of U\e type
that is often used with com-
puters is 110 bits per second.
This makes each bit last exact-
ly 1/110 second, or 9.09 milli-
seconds. The 110 bit-per-
second rate is only a maximum,
reached when characters are
sent continuously. Obviously
when there is a large space be-
tween characters, the number
of bits per second might go as
low as zero if the characters
come every half hour or so. But
the time for each bit is still
1/1 10 second, and the system is
still called a 110 bit-per-second
system. The word baud is often
incorrectly used instead of bit
per second, and so this is often
called 110 baud transmission.

Other popular baud rates are
150, 300, 600, 1200, 2400, 4800
and 9600. You can find the time

per bit by dividing the baud rate
into 1. Thus at 300 baud each
bit lasts 1/300 second, or 3.33

milliseconds.

The speed of 110 baud is
usually only used with me-
chanical Teletype machines; if
an electronic CRT terminal is
used, then more often a higher
speed such as 300 baud or even
faster is used. This concept is
important because it also
determines the number of stop
bits.

In a Teletype machine, a
clutch disables a rotating shaft
at the end of each character. In
order to give this clutch enough
time to operate, there must be
an extra few milliseconds be-
tween characters. Hence at 1 10
baud, the speed used by me-
chanical Teletypes, there are
always two stop bits used to
give this extra time. At higher
speeds, however, only one stop
bit is usually used.

From this information you
can figure out how many
characters can be sent per sec-
ond. At 110 baud, each char-
acter requires 1 1 bits (one start,
eight data and two stop bits),
so that we can send a max-
imum of 10 characters per sec-
ond. This happens to be the
maximum speed of a model 33
Teletype. At 300 baud, on the
other hand, we need only 10
bits per character (one start,
eight data and one stop bit), so
we can send up to 30 characters
per second.

Unless you have an
oscilloscope, there is no easy
way to observe asynchronous
data at 110 baud or faster. But
we can still generate it at a
s)ower rate and observe it or\ ar\
LED or on a meter. There are
two ways of doing this— with a
multiplexer or with a shift
register.

Fig. 6 shows a circuit that
could be used to generate asyn-
chronous data with a multiplex-
er. It uses circuits you've
already seen: the 555 timer,
which is being used to generate
a clock signal, was already cov-
ered in Experiment #12; the
74150 multiplexer was covered
in Experiment #44; and the 7493
is similar to the binary counter
you built with 7473 flip-flops in
Experiment #50. Since it's been

almost a year since you did
those experiments, you may
want to go back over them to
review these ICs.

We're not really going to
build this circuit, but it's a good
one to discuss anyway. Sup-
pose that initially the switch
between the 555 clock and the
7493 counter is open, so that

through 9 of the multiplexer,
with the rightmost bit going to
the number 2 input and the left-
most, or parity, bit going to the
number 9 input. Since the
multiplexer is still set to input 0,
nothing will happen at the out-
put.

But now close the switch be-
tween the 555 clock and the

A ONE IS SENT

BETWEEN

CHARACTERS

8 DATA BITS -
I

ONE OR TWO
STOP BITS

1 m
i i i
i i

i i ' i

ONE
START BIT

I I
I I

PARITY
BIT

I CHARACTER

\ 1 t /

NEXT CHARACTER
COULD START HERE

Fig. 5. The letter E as sent over a serial asynchronous line.

♦ 5V

PARALLEL DATA {

+ 5V
* 1

I
2

74150
MULTIPLEXER

D C B A

555
CLOCK

OUTPUT

7493
COUNTER

RESET

Fig. 6. Generating asynchronous data with a multiplexer.

the counter is getting no input.
Assume also that by putting a
pulse on the counter's reset in-
put we've reset it back to a
count of 0000, which is
therefore being sent over to the
74150 multiplexer.

The multiplexer selects the
input, which is connected to
+ 5 volts, and sends it to the
output. Actually, the 74150
does a built-in inversion, and so
the output signal is grounded,
rather than at a high level. But
the inverter connected to the
output inverts it back into a
high or 1. Thus the asynchro-
nous output is normally a 1 or
mark level between characters.

Now let's connect an eight-
bit ASCII character to inputs 2

7493 counter. As clock pulses
start arriving at the counter, the
counter will start counting up in
binary: 0001, 0010, 0011 and so
on. Each count is being sent to
the multiplexer, and so the
multiplexer starts scanning its
inputs, going down the line
from input 1 down to 15.

First, it samples input 1,
which is grounded, and so the
output of the multiplexer is a 1;
therefore, the inverter sends
out a 0. This is the start pulse.

Then, in turn, it samples each
bit of the parallel data, one bit
at a time, starting with the
rightmost digit of the ASCII
code and ending with the parity
bit. After that, it reaches the six
inputs connected to +5 volts,

and this is a 1 output, which is a
very long stop pulse.

Since the counter is a binary
counter that counts to 15, it
samples all the inputs. If we
use a counter that only counts
to 11, then we will only get
two ones at the end.

This is a very useful circuit,
since if we just jumper the
parallel data inputs to ground
or + 5 volts, we can use this as
a test-signal generator to
generate a continuous string of
characters. But in a computer
system it is not very practical
since it requires some sort of a
holding register to hold the
eight-bit ASCII code during all
the time that it is being sent out
by the multiplexer. This requires
eight flip-flops in addition to
the multiplexer, whereas with
the right circuit we can make do
with just the flip-flops. Still, it is
an interesting circuit to study.

That brings us to the shift-
register approach. In the shift
register, we have a group of flip-
flops that can be loaded in
parallel from the computer with
the ASCII character. But then,
after being loaded, it can shift
them out the end, one by one, in
serial.

Procedure: The first thing we
need is a shift register that can
be loaded in parallel. In Experi-
ment #46 you already built a
shift register using 7474 dual D
flip-flops. In case you don't
remember, the circuit had all
the flip-flop clock inputs con-
nected together, and the Q out-
put of each flip-flop was con-
nected to the D input of the next
flip-flop to the right.

A shift register can also be
built from 7473 or 7476 flip-
flops. Fig. 7 shows the circuit
for the 7476 dual J-K flip-flops.
Notice how the J and K inputs
of each flip-flop are connected.

The leftmost flip-flop has its
J input connected to + 5 volts
and the K input to ground. Thus
when a clock pulse arrives, this
flip-flop will set. Each of the
other flip-flops is connected to
the one to its left, so that when
a clock pulse arrives, a bit in
one flip-flop will move right into
the next one. This is how the
shifting is done to the right;
eventually the number in the
shift register will shift com-

+ 5V

1 J

-C CP

K Q

15 9

J Q

K Q

SERIAL
OUTPUT

+ 5V • PIN 5
GND = PIN 13

SHIFT
CLOCK
PULSES

Fig. 7. Building a shift register out of 7476 dual J-K flip-flops.

PARALLEL
DATA >

INPUT

S/L

SHIFT/LOAD >
INPUT

CLOCK v
INPUT '

LOAD CONTROL

SIGNAL TO
v OTHER FLIP-
7 FLOPS IN

SHIFT

CLOCK PULSES
TO OTHER
FLIP-FLOPS IN
SHIFT REGISTER

Fig. 8 A 7476 flip-flop wired as a presettable shift register.

pletely out the right end.

To output eight-bit char-
acters, we really need ten
flip-flops: The first one will
generate the steady 1 or mark
signal, the second will generate
the start pulse and the next
eight will generate the ASCII
data. We don't need any flip-
flops for the stop bits, since we
have the leftmost flip-flop con-
nected so that it will shift a 1 in-
to itself at each clock pulse.

Unless you have a good sup-
ply of 7473, 7474 or 7476 ICs,
you probably will not be able to
build such a long shift register.
Save one 7473 or 7476 for later
and build as much of a shift
register as you can with the
rest.

Our next problem is to con-
nect these flip-flops so they
can be simultaneously loaded
from a parallel port. The easiest
way to do it on your breadboard
is with jumper wire, which you
use to ground the set and clear
inputs of the flip-flops to set or
clear them. This is convenient
with the 7474 and 7476 flip-
flops, which have both set
(preset) and clear (preclear) in-

puts; with the 7473 it is a little
tougher since it only has the
clear input. But if you
remember that a 1 is shifted in-
to the register from the left, you
realize that after the first
character is sent, all the flip-
flops will already be set, and
therefore it is only necessary to
clear the ones that should con-
tain a 0.

In real life, though, you can't
expect somebody to sit there
with a wire jumper, setting and
resetting flip-flops. There has
to be a circuit to load them with
the required parallel data when
needed. Fig. 8 is a good exam-
ple. Fig. 8 shows the circuit for
just one flip-flop of the shift
register; parts would have to be
duplicated for each of the other
flip-flops.

The shift register now has a
control input labeled shift/load.
When this control signal is
high, the register shifts. When
it is low, it loads the parallel
data.

Let's start looking at Fig. 8
with the shift/load input as-
sumed high. This enables gate
1 so that the clock input can get

to the CP (clock pulse) input of
this flip-flop and all others in
the register. At the same time,
the shift/load signal is inverted
into a low and sent to gates 2
and 3, which therefore are
turned off and provide a high
output. This does nothing,
since both the set and clear in-
put of the flip-flop require a low
signal (that is what is meant by
the small circle on the input).
So with the shift/load input
high, the register just shifts.

But let's suppose that the
shift/load control input goes
low. Now gate 1 is turned off
since one of its inputs is a low,
and therefore no flip-flop can
get a clock pulse. So shifting
stops. At the same time, the
shift/load is inverted into a high
and applied to gates 2 and 3,
which are therefore enabled

Notice now that the parallel
data input is applied directly to
gate 2 and through an inverter
to gate 3. One of these will
therefore get a high level and
the other a low level. If the
parallel data input is a high or 1,
gate 2 will have a low output
and set the flip-flop, while gate
3 will have a high output and do
nothing. But if the parallel data
input is a 0, then the flip-flop
will reset.

If the parallel data changes
while the shift/load signal is
low, then the flip-flop will also
change. But once the shift/load
goes high, the flip-flop will stay
in whatever state it was in last,
and then the entire register will
start shifting.

This happens to be a very
popular circuit, since parallel-
to-serial data conversion is very
common. In fact, there is a
presettable eight-stage shift
register IC, the 74165, which has

eight flip-flops and all of the cir-
cuitry to parallel load them or
shift. The pin-out of the 74165 is
shown in Fig. 9. It works exactly
like the circuit we just de-
scribed for Fig. 8, and the
shift/load circuit has the same
form.

To generate our ASCII, we
could use two 74165s con-
nected end to end, with the SI
or serial input of the right one
connected to the Q output of
the left. But for demonstration
purposes, the simple register
you have already built out of
some flip-flops is good enough.

The last thing we need is a
control circuit to operate the
shift register properly. We need
a circuit to provide the proper
handshaking with a comp iter
port, control the loading tnd
shifting of the register and also
provide the right number of
shift pulses at the right speed.
This is shown in Fig. 10.

To analyze Fig. 10, start at
the top. Here we have the shift
register— just blocked in since
the exact circuit will depend on
the particular ICs you use.
Down near the bottom we have
an input labeled 2X CLOCK.
This is a clock pulse signal
from some clock oscillator,
which has a frequency twice
what we need, indicated by the
2X. This frequency is fed into
the clock flip-flop, one half of a
7473, which divides it by two to
get the correct frequency.

For instance, to transmit at
300 baud, we would start with a
clock that operates at 600
pulses per second. This clock is
then divided by 2 into 300
pulses per second, and this is
applied to both the shift
register clock inputs as well as
to a 7490 counter.

PARALLEL DATA INPUTS

SERIAL
INPUT

♦ 5

6 |l6

ABCDEFGH

CLOCK

74I65

S/L

Oh"

GND

CLOCK
INPUT

' SERIAL
7 . OUTPUT

SHIFT/LOAD
INPUT

Fig. 9. Pin-out of the 74165 parallel-in/serial-out shift register.

But there is a catch— notice
the vwe running down to the
clear input of the 7473 from the
other flip-flop, called the ready
flip-flop. If this flip-flop is set,
meaning that the circuit is
ready for the next character,
then the signal going down to
the clock flip-flop is a low level,
and the clock flip-flop has to
stay reset. So then nothing
happens.

During the ready state, then,
there is no shifting. Actually,
there is no shifting for a
second reason, too— the same
low signal is being applied to
the shift/load inputs of the
register and holds it in the load
state. But in your experiment,
this need not concern you since
you do not have a shift/load in-
put on your shift register.

While all this is happening,
the ready flip-flop's Q output is
high and is sending a READY
signal back to the computer.
This high signal is also going to
the reset input of a 7490 decade
counter, keeping it reset to
0000. (More on this later.)

Now let's say that at some
point the computer wants to
send out an asynchronous
ASCII character. First, it sends
it out in parallel to the shift
register, which simply loads it
into the flip-flops. (In your ex-
periment, you will take this part
by setting or resetting the flip-
flops by hand.) Then it sends a

negative-going START pulse to
the preclear input of the ready
flip-flop.

Now the circuit finally starts
to work. The START pulse
clears the ready flip-flop. This
does four things: (1) the READY
signal to the computer goes
low, telling it that the circuit is
no longer ready; (2) the reset
signal to the 7490 counter also
goes low, releasing it from its
reset state; (3) the shift/load
signal goes high, letting the
shift register shift when it gets
clock pulses; (4) the same
signal goes down to the clock
flip-flop, and its clear input
goes high . . . this stops
holding this flip-flop reset.

Everything now waits for the
next clock input to come in. As
soon as it does, the clock flip-
flop will start to work, and clock
pulses will start reaching the
shift register.

But these same clock pulses
are going to the 7490 counter.
This is a decade counter, mean-
ing that it counts by 10. Actual-
ly, it counts up to 9 or 1001, and
then on the next count it resets
itself back to 0000. After exact-
ly ten shift pulses, its last flip-
flop (which feeds the D output
on the diagram) will go from 1
toO.

But notice how this D signal
goes back to the clock input on
the ready flip-flop; moreover, its
J input is connected to +5

LOAD

XMIT
CLOCK

SHIFT REGISTER

SERIAL

ASCII

OUTPUT

TO
COMPUTER <

CLOCK
INPUT

♦ 5V

2,3,6,7,10

PARALLEL
INPUT

SERIAL
INPUT

READY

FINISHED

TRANSMITTER

RECEIVER

RESET
STOP BITS

NUMBER OF BITS

♦ ♦

SERIAL
OUTPUT

PARALLEL
OUTPUT

CHAR ACKNOWLEDGE
HAR RECEIVED

PARITY TYPE
PARITY (YES-NO)

ERROR OUTPUTS
XEIVE CLOCK

CONTROL SIGNALS
COMMON TO BOTH
TRANSMITTER AND
RECEIVER

Fig. 11. Typical pins on a UART.

Fig. 10. Control circuitry for a parallel-to-serial asynchronous
transmitter.

volts, and its K input is ground-
ed. So at the tenth clock pulse,
just as the 7490 counter
changes from 1001 (nine) to
0000 (zero), the ready flip-flop
again sets. This stops
everything dead and sends the
READY signal back to the

computer.

Here we have a circuit that

shifts out exactly ten bits and

then signals the computer that

it's done and ready for the next

character.

You may wonder why we
used a 2X clock and a flip-flop
to divide it back down again.
We could have used a 1X
clock— meaning one that ran
at the right frequency— and
started and stopped it by send-
ing it through a gate that had
the shift/load signal on the
other input. This would have
worked; but not always reliably.

It's a matter of timing. Sup-
pose that the computer sent
the START signal at the exact
time that a clock signal came
from the clock. The shift/load
might arrive just in time to let
just part of the clock signal
through the gate. The resulting
strange waveshape of the clock
might be good enough to
operate some flip-flops but not
others in the register or 7490
counter. Then things might not
work quite as expected. The
best way to avoid problems
such as this is with a circuit like
this one.

Wire up the circuit of Fig. 10
and add it to the shift register.

For clock pulses, use the pulser
on your breadboard console
and pulse the clock flip-flop
slowly enough so you can
observe the output of the
rightmost flip-flop on an LED or
a meter. Also connect an LED
to the output of the clock flip-
flop and the ready flip-flop, so
you can see how they operate
and so you can also count the
right number of clock pulses.

If you do not have a 7490
decade counter, you can use a
7492 divide by 12, a 7493 divide
by 16 or even make up your own
counter from some flip-flops.
But if you do use separate flip-
flops, use the shift/load signal
to reset the counter if the flip-
flops require a low level rather
than a high to reset to zero.

When you do this experiment,
you will not be able to generate
an entire eight-bit ASCII
character since you probably
have fewer than ten flip-flops,
but at least you will have a
chance to see how the control
circuit works. Moreover, this
circuit is a good example of
parallel handshaking with a
computer, since it has both a
START signal as well as a
READY status signal.

The UART

The circuit in the previous ex-
periment is fairly complicated,
but it's still much simpler than
the circuit you would need to
receive asynchronous data
rather than transmit it. Receiv-
ing involves quite a bit more,

because it requires that you
adapt to the timing of the
sender, rather than just send
out the data at your own speed.
Up until a few years ago,
designers had to make their
own asynchronous ASCII
transmitters as well as receiv-
ers. But now all that has
changed with the UART, or
universal asynchronous
receiver transmitter.

The UART (about $5-10) is a
40-pin IC that can both receive
and transmit asynchronous
data. Fig. 11 shows the con-
nections to a typical UART. The
unit has two more-or-less in-
dependent parts— the trans-
mitter shown at the top and the

receiver shown at the bottom.

The transmitter accepts a
parallel input of up to eight bits
and provides a serial output. It
requires an external 16X clock,
which must run at 16 times the
baud rate. For a 110 baud
signal, for instance, the clock
must be at 1760 pulses per
second. The transmitter also
has a LOAD input and READY
and FINISHED outputs, which
would go to the computer's
parallel port.

The receiver is the reverse of
the transmitter— it inputs a
serial asynchronous signal and
outputs a parallel character. It
has a 16X clock input, as well
as two handshaking signals— a

CHARACTER RECEIVED output
and CHARACTER ACKNOWL-
EDGED input. It also has three
error outputs, which provide a
signal to the computer if some-
thing goes wrong.

The UART is a versatile cir-
cuit that can be used in various
ways by being set to various
operating modes with a number
of control signals common to
both the transmitter and the
receiver. These can select the
type of parity, the number of
bits sent and the number of
stop bits.

We won't go into the UART in
great detail since it has been
covered in a variety of other ar-
ticles. If you are interested in

serial and parallel computer
communications and more in-
formation on the UART, a good,
inexpensive book is the TV
Typewriter Cookbook by Don
Lancaster, available from the KB
Book Nook and at Radio Shack
stores.

Preview

Next time we will continue
our discussion of computer in-
put and output, but from the
computer side rather than the
I/O device side. We will see how
handshaking and data transfer
are handled by various proces-
sors. Most interesting, we will
look at interrupts. See you
then!!

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Point of Sale/Inventory
Control System for 8080s

Businessmen— for approximately the equivalent cost of one year's salary for
a single clerk, you can now have POSIS, a complete inventory control system.

Bruce A. Barker, President
The Data Group, Inc.
8077 Bramwood Ct.
Indianapolis IN 46250
(317)634-4784

A financial genius, an indus-
trial guru or another per-
son of exceptional insight is
not required to forecast the
most promising market for the
majority of current computer
stores.

The personal computer mar-
ket offers little promise to the
computer store. If the wide-
spread market for appliance
computers exists, and there are
serious doubts that it does, this
market will likely be dominated
by mass retailers. Large retail
operations (Radio Shack is a
perfect example) can mass-
produce inexpensive personal
computers in quantities far
greater than most computer
stores can even dream of.

The hobby computer market
offers little additional promise.
Outside of the few areas where
there are high concentrations
of technically oriented individ-

uals, there are simply too few
people to support more than
one hobby computer store.

Besides, the technically
oriented hobbyist often tends
to be the type of person who
does not require, and is not will-
ing to pay for, the support a
computer store offers. The
technically oriented hobbyist
would rather save a few bucks
by ordering a bare board from a
mail-order house and ap-
propriate the chips from work.
The bottom line is that most
hobbyists simply do not spend
the type of dollars necessary to
keep a store in business.

By far the most promising
market for the majority of the
current crop of computer
stores is the vast number of
businesses and schools that
are literally crying for profes-
sional-quality computer hard-
ware, complete service support
and well-designed application
software— all at a reasonable
price. A few manufacturers are
currently producing products
that fill the need for reliable,
professional-quality hardware.
Several computer stores are

now, or will shortly be, ready to
provide the support a business
demands. It is now past the
time for the industry to produce
well-designed application soft-
ware to be made available for
either off-the-shelf delivery by
local computer stores, or as a
basis for field modifications by
the local computer store.

The Data Group, Inc., has
been predicting these develop-
ments in the microcomputer
market since late 1976. It was
our own need for good busi-
ness software, and an acute
awareness of the needs of the
industry, that led us to begin
devoting the majority of our
energies to producing the kind
of business software that will
help open this vast market to
our fellow computer stores.

Inventory Control— Every
Business Should Have It

For many businesses, par-
ticularly the retail and whole-
sale businesses for which
POSIS was designed, the larg-
est single asset item, by far, on
the balance sheet is the invest-
ment in inventory. You cannot

overemphasize the need for a
business to keep tight controls
on its largest investment. One
of the keys to the success of
many small businesses is to
maintain inventory at such a
level that a minimum amount of
costly capital is invested, yet
still keep a sufficient stock of
the right kinds of products on
hand and available for delivery.

The vast majority of small
and medium-sized businesses
still use the slow, costly, inef-
fective manual systems, if they
maintain any inventory records
at all. These systems generally
require one or more clerks to
laboriously take mlormation
from documents recording the
sale and delivery of inventory
and write the information onto
some sort of file card. In the
rapidly moving business world
of today this method is clearly
unacceptable.

The problems with manual
inventory systems are many.
One of the most obvious prob-
lems is the lack of timely ac-
cumulation of information. In a
business with even a moderate
number of daily transactions, it

1. 8080 or Z-80 based, S-100 bus microcomputer.

2. 48,000 bytes RAM addressed 0000 H-BFFF H.

3. One Micropolis dual-drive floppy-disk system (630,000 bytes
of disk storage). A copy of Micropolis Disk BASIC Version 3.0
is also necessary.

4. An interface board with at least one RS-232 C port. Addi-
tional parallel or serial ports may be necessary depending
on the type of printer (if any).

5. One serial video terminal (a Soroc IQ 120 is recommended).

Fig. 1. Hardware requirements to use POSIS (standard system
configuration).

is certainly not unusual to find
that information on the inven-
tory file cards is as much as
several days to several weeks
out of date. Perhaps the only
thing older than yesterday's
news is yesterday's, or last
week's, stock list. Up-to-date in-
formation is absolutely vital to
a well-run inventory-control
system.

Manual inventory systems
are subject to all manner of
human errors, ranging from er-
rors in addition or subtraction
to information recorded on the
wrong file card. Even the best
posting clerks make mistakes,
which, at best, require a great
deal of time to find and correct
or, at worst, can cause lost
sales due to the lack of an item
in stock. Accurate information
is absolutely vital to a well-run
inventory-control system.

I could easily write pages on
the inadequacies of manual in-
ventory information systems.
Most businessmen, however,
are quite well aware of the inef-
ficaciousness of manual sys-
tems and probably do not need
or want to be reminded of such
problems.

Microcomputers to the Rescue

POSIS, when used with a
microcomputer system, allows
small-to-medium-sized retail
or wholesale businesses to use
computers to put an end to the
inefficiencies of manual inven-
tory systems. The benefits of
computerized inventory control
using microcomputers are
many; the risks and costs are

few.

For many businesses the
primary reason to switch to a
computer is to eliminate the
need for additional personnel.
When you figure the cost of

wages, employment taxes and
miscellaneous costs, a clerk of
minimum competence will cost
at least $10,000 per year, prob-
ably more. A microcomputer
using properly designed soft-
ware will, in many cases, allow
a company to process far more
transactions without the need
for additional personnel.

That a computer increases
the efficiency of a business has
been proven so many times
that I will not waste time with
examples. Since a microcom-
puter with POSIS will probably
cost less than $10,000 and will
certainly replace at least one
additional person, the payback
period will be one year or less.
When you add in tax advan-
tages, such as the 10 percent
investment tax credit, the total
cost of the system is reduced
even further.

POSIS, A Summary
off its Features

There are many reasons why
we at The Data Group think
POSIS is a major step forward
in microcomputer-based busi-
ness software. One of the most
important is the basic philoso-
phy behind POSIS. When we de-
sign a computer-based infor-
mation system we do just that
— design an information sys-
tem. It just so happens that the
tool we use to store and manip-
ulate the information is a com-
puter. The distinction we are at-
tempting to draw here is be-
tween writing a computer pro-
gram to produce business in-
formation and designing an in-
formation system around a
computer.

It has been our experience
that computer programs to pro-
duce business information
tend to be written by program-

mers for programmers and, as
such, fail to include many vital
features. Our philosophy of de-
signing an information system
using a computer means that
we approach the problem by
realizing that clerks, managers
and accountants, not program-
mers, are going to be the
primary users of the system.

A computer system that is
meant to be used in an environ-
ment where the majority of
users are unfamiliar with com-
puters must be totally interac-
tive with the user. In other
words, the computer must con-
verse with the user in plain
English, not in computer
jargon. We consider this a
prime factor in making POSIS a
workable system. Aside from a
couple of BASIC commands
used to load POSIS into the
computer from the floppy disk,
POSIS leads the user every step
of the way through the use of
standard English.

In many computer programs
currently available for micro-
computers, we have found that
there are many times when the
user could easily be dropped out
of the middle of the program be-
cause of a simple error in enter-
ing data. Many users, when con-
fronted with an error message, a
program line number, and a pro-
gram statement, would have ab-
solutely no idea what to do next.
Futhermore, they would have no
idea, and no way of finding out,
what information had been
altered before the program
crashed and what information
still had to be entered. This is
totally unacceptable in a busi-
ness environment.

POSIS contains the most ex-
tensive error-handling capabil-
ities we have seen to date in
microcomputer software. With
POSIS, there are only a couple
of obscure instances when an
operator error could crash the

program, and these errors are
specifically stated in the in-
struction manual. In some
cases POSIS will even question
and refuse to accept informa-
tion, such as unbalanced jour-
nal entries, that is obviously in
error.

Security of both the com-
puter itself and the data within
the system is of prime concern
in POSIS. Before a person is
allowed to see the main menu
(the list of possible functions
within the system), a valid
employee ID code must first be
entered and verified by POSIS.
When the employee has
chosen which operation he
wishes to perform, he must
then enter the proper password
for that operation.

Various operations are avail-
able to different employees de-
pending on their level of
authority. To prevent an em-
ployee from just sitting at the
terminal and trying various
combinations, the system will
allow only five attempts to
enter either the employee ID or
password before denying that
person access to the system
and recording the attempted
breach of security.

The vast majority of user er-
rors that could cause destruc-
tion of information stored on
the disks have been anticipated
and are handled by the system.
Further integrity of the data
has been achieved by a simple,
yet complete, regime of main-
taining backup copies of all
data that might be subject to
destruction.

In addition, we use the trans-
action diskette method of stor-
ing the information that is en-
tered into the system. The data
entered into the system is
recorded on one particular
diskette which, at the end of the
day, is used to update informa-
tion on a permanent accounts

1. A hard-copy device (printer).

2. Additional 12,000 bytes RAM.

3. Additional Micropolis dual-drive floppy-disk system (total of
1,260,000 bytes disk storage).

4. Additional video terminals and associated hardware. Note:
Access to the computer by additional terminals will be
serial, that is, only one terminal will be able to access the
system at any one time. All other will wait.

Fig. 2. Optional hardware.

diskette. In the unlikely event of
a power failure or other major
interruption in the use of the
system, the permanent infor-
mation on the accounts disk-
ette and other records generat-
ed either by the system or man-
ually can be used to recon-
struct the lost data.

In the writing of computerized
information systems, one per-
son who almost always seems
to be overlooked is the accoun-
tant. POSIS was designed by an
accountant with the needs of
the auditor or accountant in
mind. POSIS records a sum-
mary of each and every piece of
information entered into the
system and provides a clear,
easy-to-follow audit trail in
order that an independent audi-
tor may verify the accuracy of
the information stored in the
computer.

Double-entry accounting,
balancing the debits and
credits, is universally accepted
in the United States as the
proper accounting method.
This may seem to be a self-
evident statement; however, it
is one that must be considered
in designing an accounting sys-
tem. All accounting informa-
tion contained in POSIS is in
the form of offsetting debits
and credits. This provides
another self-check within the
system against both human
and hardware failures.

From the viewpoint of the ac-
countant, an area of prime con-
cern is that an inventory control
system maintain an accurate,
consistent and sound method

NAME

STORAGE FORMAT

# DIGITS (CHARS)

Manufacturer Code

XXX

Item Code

xxxxx

Special Order Code

Product Description

xxxxxxxxxxxxxxx

Retail Price/unit

XXXXX. XX

8(incl7)

Min Stock Level

xxxxx

Max Stock Level

xxxxx

Current Cost/unit

XXXXX. XX

# in Stock (current cost)

xxxxx

Previous Cost/unit

XXXXX. XX

# in Stock (previous cost)

xxxxx

Last Order Date (purchase order date)

xxxxxx

# Ordered— Last Order Date

xxxxx

Tot # Ordered— Not Recv'd

xxxxx

Tot # Back Ordered

xxxxx

3000 unique products may be stored with the standard system configuration. The addi-
tion of the optional dual-drive floppy-disk system will increase the number of products
by 9000.

Format

Account #

Account Name

x,xxx,xxx.xx

102

Cash

xxx,xxx,xxx.xx

120

Inventory

XXX, XXX. XX

129

Inventory receivable

x,xxx,xxx.xx

201

Purchases

XXX, XXX. XX

260

Deposits received, goods not delivered

XXX, XXX. XX

250

Sales tax payable

xx,xxx.xx

280

Charge-card fee payable

xxx,xxx,xxx.xx

8100

Sales

x,xxx,xxx.xx

8130

Service

xxx,xxx,xxx.xx

8200

Tax-exempt sales

x,xxx,xxx.xx

8230

Tax-exempt service

xxx,xxx,xxx.xx

7100

Cost of goods sold

XXX, XXX. XX

7370

Charge-card expense

XXX, XXX. XX

7110

Incoming shipping expense

xxx,xxx,xxx.xx

9010

Loss due to theft, damage, etc.

of placing a value on the inven-
tory. A great deal of thought
has been put into the inventory
valuation method POSIS uses.
Since most businesses use a
FIFO (first in-first out) method

Items over or under maximum/minimum stock level (items
needing to be reordered).

2. Stock reports.

a. Price List.

b. Full report of all information stored on each item.

3. Recall sales receipts by receipt number, or list all sales
receipts.

4. List summary of all transactions entered on a diskette.

5. List attempted security breaches.

6. List items on back order.

7. The following sales analysis reports will be available in
future updates: (those with * are now available)

*a. Inventory mix report (percent of total inventory represent-
ed by each item).

*b. Sales mix and turnover. Percent of total sales represented
by the sales of each item. Number of units sold per month.

c. Gross margin analysis. Percent of total gross profit repre-
sented by the individual gross margins of items sold.

d. Other reports may be added as requested.

Fig. 5. Reports generated.

of inventory valuation, this is
the valuation method we chose
for POSIS.

It is also important to remem-
ber that in actual business
situations a product may be in
stock at more than one price.
While the details of how POSIS
handles multiple levels of in-
ventory costs are very lengthy,
it is important to know that
POSIS recognizes the prime im-
portance of inventory valuation.

One of the major complaints
about the entire microcomput-
er industry is that there is a
severe lack of proper documen-
tation. POSIS comes with an
extensive user's manual that
not only explains in detail the
operation of POSIS, but also
devotes considerable material
to the use of POSIS as part of
an accounting and manage-
ment information system.

Additional documentation

available to distributors and
dealers includes a completely
documented programmer's
manual with flowcharts, infor-
mation about the structure of
the data files and other infor-
mation necessary to proper
field maintenance and modi-
fication.

The accompanying figures
provide an overview of POSIS.
Fig. 1 lists the hardware con-
figuration necessary to run
POSIS; Fig. 2 lists optional
hardware that POSIS can use;
Fig. 3 lists the information
stored on each item; Fig. 4 lists
the accounting information
stored in POSIS; and Fig. 5 lists
the reports generated by POSIS.

POSIS is now available for
delivery to individual users at a
cost of $750. Dealer inquiries
are welcome. The Data Group,
Inc., 8077 Bramwood Ct., In-
dianapolis IN 46250. ■

Shack

This ad just might make you a believer.

You can't beat
the 4K system at

$599

TRS-80 "Breakthru"

• TRS-80 microcomputer

• 12" video display

• Professional keyboard

• Power supply

• Cassette tape recoder

• 4K RAM, Level-I BASIC

• 232-page manual

• 2 game cassettes

. . or the step-up
16K system at

$899

TRS-80 "Sweet 16"

• Above, except
includes 16K RAM

... or the fast
4K/printer system at

$1198

TRS-80 "Educator"

• Above, except
includes 4K RAM and
screen printer

..or the Level-ll

16K/printer/disk
system at

$2385

TRS-80 "Professional"

• Above, except
includes 16K RAM,
disk drive, expansion
interface, and
Level-ll BASIC

So how are you gonna beat the system that
does this much for this little? No way!

. . . The amazing new

32K/Level-ll/2-disk/

line printer system at

$3874

TRS-80 "Business"

• Above, except
includes 32K RAM,
line printer,
and two disk drives

Get details and order now at Radio Shack stores and dealers in the USA, Canada, UK, Australia, Belgium, Holland, France, Japan.
Write Radio Shack, Division of Tandy Corporation. Dept. C-053, 1400 One Tandy Center, Fort Worth, Texas 76102. Ask for Catalog TRS-80.

Radio /hack

The biggest name in little computers

Financier/Mortgage with
Prepayment (from Instant Software)

It's fun to toot your own horn once in a while. This unsolicited (no kidding!) review
describes and evaluates a pair of PET programs from our Instant Software line.

O. Borland

36 Ainsdale Rd.

Toronto, Ontario M1R 3Y8

Both programs are pre-
recorded on one cassette,
nicely packaged in a hard paper
box with imprinted names of
the progams. A small booklet
containing the program listing
and instructions on how to run
the programs is enclosed.

The first program, "Finan-
cier," is definitely the best and
the most useful financial ap-
plication I have seen so far on
personal computers. It can per-
form ten different financial cal-
culations, such as one-time in-
vestments, regular deposits, re-
maining balance on a loan, etc.

The program is truly self-ex-
planatory, and I could operate it
even without looking at the
enclosed booklet. After I typed
in "RUN," the program dis-
played the heading with the
program name and description,
and then it advanced to the next
screen with a list of the avail-
able financial groups (invest-
ment, depreciation, loans). I
first selected the "Cost of Bor-
rowing" option in the loan
group, and then I ran it several
times, varying the interest rate
and term of loan, trying to find
the lowest cost. Also, the other
options are quite useful, partic-
ularly the investment group
with the breakdown of invested
capital, accumulated interest
and the total value.

Operating the program for
the first time, I was confused
about the correct input for the
term of investment. As I en-

tered the full year only, another
prompt for the number of
months was produced. This de-
notes that when the term is en-
tered, both the years and
months are to be entered and
separated by a comma.

The entire program resides in
about 7K, and after the alloca-
tion of the variables, I found
there were only 20 bytes left in
the memory. However, the pro-

execute surprisingly fast. The
screen layout is neat, and the
formatting of the displayed
results is nicely arranged. I
especially liked the alignment
of the monetary amounts in the
breakdown and totals.

The second program will be
of use primarily to people con-
templating the purchase of a
home or currently financing a
mortgage. First it calculates

INSTANT SOFTWARE

Mortgage with
Prepayment

and Financier

by Microcosm

ENTER THE PRINCIPAL AMOUNT :? 755

ENTER MORTGAGE TERM (YEARS) ? 10

ENTER ANNUAL INTEREST RATE '.? 15

NUMBER OF PAYMENTS PER YEAR :? -

REGULAR PAYMENT $121.91

TOTAL TO BE PAID $14518.69

COST OF THE MORTGAGE: $7818.69

DO YOU WISH TO PREPAY YOUR MORTGAGE ~>

0006P Instant Software Inc., Peterborough NH 03468 USA See ruvene tor progrem information

gram doesn't make use of over-
lays, as some of the bigger pro-
grams do, and thus the entire
program resides permanently
in the memory. Because of the
size, it takes rather long to load
the program into the memory
(about two minutes). Once the
program is in the memory, it will

and displays the regular
payments on a loan or mort-
gage. In contrast to other mort-
gage programs, this program
demonstrates the savings
resulting frorn paying the anni-
versary prepayments on the
mortgage.

I was surprised to learn that

if I borrowed on a short-term
loan for the prepayments, even
at a higher interest rate than
the original mortgage, I could
experience a savings.

Well, if you are thinking
about purchasing a house or
condominium, then you would
be well advised to invest first in
this program and a PET, if you
don't own one yet. Then you
can run a couple of calcula-
tions, find the optimal mort-
gage and prepayment for you,
and the achieved savings will
surly justify the cost of your
computer. You may even find
enough money from the sav-
ings to upgrade your equip-
ment. There are two more op-
tions in the program— one is
the amortization schedule for a
mortgage with or without the
prepayment; the other is a
detailed explanation of how the
prepayment works. The progam
is easy to operate and the
screen layouts are well de-
signed.

Two things in this progam de-
serve comment. (1) The mort-
gage calculation employs the
simple monthly interest
method, whereas most Cana-
dian mortgage companies use
semiannually compounding
methods. (2) The progam does
not allow for variable prepay-
ments. Also, this program
seems to use a lot of memory
(there were only 101 free bytes
left over).

In summary, if you own a PET
computer this package is an ex-
cellent buy for $7.95. I suggest
you take a look at it during your
next visit to your local com-
puter store. ■

An advanced aesniop data 5»ys w?m

for $1,995? Quitcherkiddin, TANO.

We're not kiddin'.

Outpost 11 is exactly that. You get:

• A ruggedly designed unit,
intended for heavy use

• Full ASCII keyboard

• 24 x 80 character CRT

• 32K bytes RAM

• M6800 CPU

Just like this, for only

Mini-floppy disk drive and

controller

BASIC software package

Over 20 applications packages

available

User documentation

ct/rpcsr//

COMPLETE

With Outpost 11 and the BASIC software
package, you can:

Do full floating point BCD math • Pro-
gram SAVE and LOAD with file names •

Quitcherkiddin, TANO I'm calling your hand. Send me

Program MERGE andCHAIN^ON ERROR
statement • String variables and functions
• Trig and math functions • GET PUT and
FIELD statements • Floppy file processor
i — ^m ■■ mm Order Form ™™ ^™ ^™ ^™«

You've been waiting a long time for a Data
System with all these features at a price like
this. Now it's yours. No kiddin'.

*Quit your kidding

Mail to:

Outpost 11s as de-
scribed in your ad. Heres my deposit of $200 each, plus $35 freight and insurance
I'll pay the balance on delivery.

Name

T37

Company/Title

Shipping Address

| Telephone

Signature

Corporation

4521 W. Napoleon Avenue

Metairie, La. 70001

(504) 888-4884
TWX 810-591-5229

Sales Offices Los Angeles CA-21 3/426-7375 • Montreal, Canada-51 4/934-0000 • Boston, MA-61 7/969-4650 • Dallas, TX-214/
358-1307 • Houston, TX-71 3/461 -0038 • Denver. Col -303/841-2788 • San Francisco, CA-408/377-7001 • Chicago, IL-31 2/830-0060
• Atlanta, GA — 404/252-6609 • Washington, DC — 301 /593-1559 •

Hey, Kids! It's "Mickey Modem"

(Not a Toy)

We've all been waiting for this— an excitingly simple way to interconnect computers
via the telephone lines. Well, wait no longer! We feel certain that you'll love this.

Stephen Gibson

PO Box 38386

Los Angeles CA 90038

The most practical way for
computer hobbyists to
trade programs is by direct
computer linkup. Paper tape,

cassettes, disks and printed
listings are only stepping-
stones to getting the program
out of someone else's machine
and into yours. Sure you want a
copy to save for later use, but
you may have to wait until the
next computer club meeting or
a more convenient time to swap
your software.

Use your computer as a stand-alone terminal by tying the cassette
port to Ma Bell with simple software and this handy gadget.

The simple solution is to in-
terconnect your computers over
the normal telephone lines. Not
only could you trade programs,
but also you could have some
real fun with your hobby by
playing interactive games. After
all, why should you always lose
to your computer? At least you
have a chance when you play
another human!

Easier Said Than Done

Most computer-to-telephone
interfaces used today are called
modems. They convert your
computer's TTL, current loop or
RS-232 levels to tones that can
be sent over the phone lines at
a reduced error rate using a
method of frequency shift key-
ing. They generally use two
separate frequency bands for
transmission and reception. In
the Bell 103 modem, for in-
stance, 1070 Hz and 1270 Hz are
used to send, while 2025 and
2225 are used to receive.

To communicate, one hobby-
ist uses a modem like the 103
above called an "originate"
modem. The other hobbyist
must use a different modem
with opposite sets of send and
receive frequencies called an
"answer" modem.

That these terms, originate
and answer, make no sense in a
hobbyist computer-to-computer
linkup is just the tip of the ice-
berg. So far, we might need one
each! Nice redundancy, but

lousy economics because mo-
dems in general aren't inexpen-
sive. Unless you build a kit or
buy one new, you are forced to
comb the surplus market for
one with low mileage and price.
The real problem surfaces
when you discover that most
surplus modems are originate
only! Besides the originate unit,
you're going to need an answer
modem, or better yet, a combo
unit . . . and they're hard to find.
On the other hand, you could try
to modify yours to make it a
combo unit. But overall, there's
no easy way to get a modem
working without having to shell
out some cash and/or grief. At
this point you might wisely con-
sider the project a total waste
and continue trading programs
on cassette and the like.

Enter the Mighty "Mickey"

Why not send the cassette in-
terface audio directly over the
phone lines? And why can't you
connect your computer's cas-
sette port to the phone and
talk direct or play games on
each other's computers? It's
possible. In fact, it works for
most cassette I/O formats so
long as you stay with the local
phone lines. Long-distance
lines have narrower bandwidth
and exhibit other kinds of dis-
tortion that cause some cas-
sette I/O formats to not work
as well as others.

You can make a super simple
interconnection with a gadget I

call "Mickey Modem" ... be-
cause "Mickey" isn't quite a
modem. It's really two IC ampli-
fiers wired to a hybrid network
connected to your phone line.

A note of caution is in order
here. Despite recent court
rulings, you should still deter-
mine if your local phone com-
pany requires a coupler to the
line. Mickey is legal for direct
connection only in some parts
of the country.

Disgustingly Simple Circuit!

Your computer cassette port
output feeds line driver Amp A1
(see Fig. 1). The level is adjusted
by R1 for dbm on the meter.
A1 drives the phone line through
a network of resistors, R2, R3,
R4 and T1. It is here that we are
able to feed the proper level to
the line from A1 but not over-
drive the input amplifier A2 to
hassle our eardrums . . . and
the computers!

The way it all works is rather
simple. Amplifier A1 feeds the
junction of R2 and R3, and the
signal is coupled to the line via
T1. U variable resistor R4 is ad-

justed to equal the line resis-
tance presented T1, the volt-
ages from A1 that appear at
the opposite ends of R2 and R3
will be equal. Therefore, the
output of amplifier A2, wired in
a differential mode, will be zero.

So much for theory. Actually,
the best suppression you can
get is wholly dependent on line
reactance and may vary from 30
to 40 db. At worst, this is more
than adequate for a condition
here that calls for only 10 to 20
db rejection. In practice, R4 is
adjusted for an equal send and
receive level from the speaker
and simply forgotten. More on
this later.

The signal coming in from
the line is amplified by A2 and
feeds the computer's cassette
port input. It also feeds a speaker
through a 47 Ohm resistor for a
convenient volume. The .005
capacitor across R7 suppresses
noise from the line only at high-
gain settings due to the parallel
RC combination.

Easy-Construction Tips

"Mickey" can fit into any box

you may already have. After all,
2 ICs, a transformer and bat-
teries don't take up much space,
on the other hand, you might
decide to use a larger, more at-
tractive case as seen in the
photos. This would provide you
with space for sound effects or
music goodies when you add
them . . . especially since you
already have an amplifier wired
up, ready to go!

The meter and controls fit
nicely on the sloping panel of
an LMB 1042 box. The I/O con-
trol jacks are located on the
side. I put mine in the same rel-
ative position as those on a
Radio Shack CTR-41 recorder.
A TRS-80 user might find this lo-
cation very convenient. Simply
exchanging the plugs from the
recorder to Mickey Modem is all
that is necessary to interface
the TRS-80 to Ma Bell!

I assembled the circuit on a
Radio Shack 276-151 Experi-
menters PC board. A board half
this size would have worked,
but why bother if you plan to
shove it into a big box? The

transformer is mounted on a
scrap piece of aluminum and
bolted to the case with 6-32
hardware. Even though the
average local loop impedance
between your phone and the
central office is around 900
Ohms, a 600/600 Ohm line
transformer will work just fine
forTL I used a Triad A67J,buta
cheap import 600 Ohm or even
1000 Ohm unit will work be-
cause the signal is under a mil-
liwatt, and R4, when adjusted,
equalizes the slight mismatch.

The application notes for the
LM-386 IC amplifier call for a 10
Ohm resistor and a series .1 uF
RC combination to suppress an
annoying oscillation that occurs
at higher current levels. I bread-
boarded the circuit and discov-
ered that the unit works very
well without the 10 Ohm resis-
tor in this particular application.
That's two less parts to dig up.
Controls R1 and R4 can be PC
card pots. You will set them
only once.

The unit is activated by the
computer. Why not? The
TRS-80 and the Tarbell inter-

SEND

RECEIVE

INPUT
I00-IK mV

REMOTE

OUTPUT
2 VPP

♦9VDC
AT 25mA

50
I5V

OPTIONAL SWITCH

Tl = 600/600 LINE TX TRIAD A67J OR EQUIVALENT
AI.A2 '- NATIONAL LM386 . RADIO SHACK 276-173*

(LM380 WILL ALSO WORK)

-6dbm

INTO PHONE LINE

LvwJ
600/900ft

All resistors are 5% V* Watt.
All 'lytics rated over 9 V (15 V).
An import 600/600 tx will work.

The gain of either amp can be reduced from 46 db to 26 db by removing C3 or C7. R1 and R4 are audio
taper and can be mounted on circuit board. They are set only once. You may not need the VU switch.
Just hard-wire to the "receive" line. Radio Shack 276-151 PC board is a simple way to go.

Setup: Feed 400 Hz @ 100 mV rms into input and set R1 level for -6 to -10 dbm into phone line. Unit
must be connected to 600-900 Ohm load for test. (The line is a good 800-900 Ohm load !) Adjust R4 for a
minimum level on "receive" VU position. A -30 dbm 600-900 Ohm signal into the phone jack will put
about 2 V P.P. at output jack. C6 cuts noise on the line only at high volume settings. C4 and C9 cut low
end "fuzzies." TRS-80 fans should connect "ear" line to Output, "aux" line to Input and remote to
remote!

Fig. 1. Only two IC amplifiers and a hybrid network are needed to interface cassette port audio to the phone lines. The wires marked with
an "X" are possible modifications to read battery voltage after initial calibration. See text for details.

faces have this capability.
Before a cassette read or write,
a relay, operating under soft-
ware is closed and turns on the
unit. If the battery life is unim-
portant, you can simply sub-
stitute an SPST switch for the
remote jack function. I wired two
batteries in parallel . . . hardly
worth the effort because the unit
draws a paltry 25 mA.

Be sure to use shielded wire
between the circuit card and
the controls. The high gain of
the IC Amps can cause un-
wanted oscillation due to feed-
back. If you use a common
ground bus and ground all
shields at one point, you'll do
fine.

Final Operational Checkout
or Making "Mickey" Talk!

Install a spare telephone jack
next to your phone and a mat-
ing plug on the end of "Mickey's"
I/O line. "Mickey" should be
wired to the red and green wires
of the telephone jack. If the
Remote jack circuit is closed,
you should hear a nice loud dial
tone from the speaker when S1
is switched to the line. You can
test the unit with tones from
the cassette port, but I suggest
you conduct your tests back at
the bench before you connect
"Mickey" to the telephone net-
work.

Bench checkout should give
the following results. A 600
Ohm, -30 dbm RMS signal at

400 Hz fed to "Mickey's" tele-
phone line input should pro-
duce better than db on the
meter with R7 wide open. The
signal feeding the computer
will be around 600 to 800 mV
RMS and present a source re-
sistance of about 1000 Ohms.

Looking the other way ... a
100 mV signal from the computer
should be adjusted by R1 to
read db on the VU meter, which
will produce -6 to -10 dbm in-
to a 600 to 900 Ohm load con-
nected to "Mickey's" phone
line jack. You can remove C3 to
drop the gain of A1 , 20 db if your
computer output level is greater
than 100 mV.

R4 is adjusted by feeding a
signal from your computer into
the line after you've reached
another user. You simply set
the VU switch to "receive" and
adjust R4 for a minimum reading
on the meter. You are looking at
feedthrough from A1. So if the
meter is reading off scale,
simply reduce the "send" level
long enough to find a conve-
nient R4 null point. This is not a
critical control from a circuit
operation standpoint. Its pri-
mary purpose is to maintain
reasonably even speaker vol-
ume levels between send and
receive.

You may not ever need to re-
set this control, even though
you may be communicating with
several users at various dis-
tances from you because you

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A hold button cuts noise on the line during data transfers. The unit
in the photo is marketed under the name "Phone Censor" and is
easy to install between the microphone and the handle.

Mounting I/O and control jacks in the same position as the cassette
recorder makes changeover to Mickey Modem a snap. Here, the
jacks line up with a CTR-41 recorder for a TRS-80 computer.

will always be tied to the same
amplifier at the central office.
And unless the phone company
installs an extra couple of miles
of cable between you and that
first amplifier, you just set R4
once and forget it!

Some Nifty Mods

Inasmuch as the send level is
preset, you might choose to
eliminate the send/receive meter
switch and permanently wire
the unit in the receive position
once the level is set. Just be
sure all your level setting mea-
surements are made with a 600
to 900 Ohm load across the
phone jack or with the unit con-
nected to the line. Proper levels
are essential for legal operation.

Another way to utilize the VU
switch might be to disconnect
the line from the "send" posi-
tion and connect a 33k resistor
from the battery to the switch
instead. You can then check on
battery voltage without open-
ing the box. When the battery
drops below about 7 volts, the
meter will no longer read above
100 percent and tell you it's
time for a change. Adjust the
resistor size to suit your own
tastes; the VU indication is only
relative. You can operate the
unit with or without your phone
off-hook.

A useful device that's mar-
keted under several names as
seen in the photo can function
as a quickie "hold" button. It
slips between the microphone
cartridge and the handle of the
phone. A button on the side al-

lows you to shut off the mike
during a data transfer, yet al-
lows you to listen or carry on a
conversation. This is a very nice
feature when you are both de-
bugging a piece of software.
Two users can discuss various
mods, then squirt them back
and forth until either person
finds a solution.

I use a Heathkit speaker-
phone and leave it off-hook
nearly all the time. Keep in mind
that a phone that's off-hook will
load the line and lower the level.
It may even throw the network
balance (R4) off enough to be
an annoyance. While "Mickey"
has reserve gain, you still might
find you can ruin a data trans-
fer if you lift off-hook in the mid-
dle of something.

Real Software Fun!

Once you've passed the
checkout phase, you can trade
programs with ease. You simply
type "CLOAD," for instance,
while the other computer is in
the "CSAVE" mode. Other cas-
sette I/O conventions exist,
but I'm sure you get the idea.

Now for the interactive con-
nection. This next step is where
the real fun of this hobby be-
gins. To illustrate the point, I've
included an interactive pro-
gram. The only translation
problems you might have are
those relating to your cassette
I/O commands. For example,
Radio Shack BASIC software
incorporates a "PRINT #" and
an "INPUT #" command to read
and write data variables to cas-

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The circuit is assembled on an Experimenters PC board and bolted
to the case bottom with the transformer and batteries. Shielded
wires are used between the circuit board and the controls to elim-
inate feedback. Control R4 can be mounted on the board or the
rear of the case as shown. A standard four-prong telephone plug
connects the unit to the line.

sette.

Other cassette I/O commands
such as "OUT" can be easily
adapted to this TRS-80 pro-
gram. You can do it with Mits
ACRs or Tarbells to name just
two. Simply substitute the ap-
propriate cassette I/O com-
mand.

The only interactive software
difficulty that I've encountered
involves keeping track of each
user's variables and system
timing. A generous use of FOR/
NEXT loops keeps each user in
step and obviates the possibility
that one machine may enter a
data transmission mode before
the other is ready to receive.
This all happens in a fraction of
a second, and the users are
generally not aware of it . . . but
neither can they screw it up!

Interactive 23 Bytes . . . Just to
Get Your Feet Wet

The game of 23 Bytes (Yup
. . . bytes!) is a good example to
illustrate foolproof interactive
operation. The rules are simple
enough. "You see, there is this
stack of 23 bytes." The stack,
as many soon learn, is from the
top . . . down.

Anyway, someone goes first
and can remove one, two or
three bytes from the stack. The
other player takes his turn and
removes one, two or three bytes
from the stack. Each player
takes a turn, and the stack
shrinks. The player that must

take the last byte loses. Similar
versions of this BASIC program
use 23 matches or 23 cards.
Usually you play the computer
and lose . . . until now!

Program Description

The program goes through
the initialization machinations
up through line 75. The CLS

command clears the screen in
Radio Shack BASIC. The line
4000 subroutine called in line
15 gets your name and your op-
ponent's (A$ and B$). Variable J
is simply a game counter.

Someone must go first. Since
you both are operating on inde-
pendent computers, you must
make this decision ahead of
time. Naturally you could have
one computer decide, then tell
the other, but let's stay with the
basics, then branch out to other
possibilities.

Once you decide who goes
first and have entered it in the
program Z, the computer then
enters one of two routines be-
ginning at line 100. If you were
to go first, Z would be 1 on your
machine, but it would be 2 on
your opponent's. Based on the
value of Z, your computer would
enter the "Your Turn" subrou-
tine at line 1000, while your op-
ponent's machine enters the
"Opponent's Turn" routine at
line 2000 because the value he
input to Z was 2.

Each computer trades off the
value of Z (1 or 2) between each
of you as you each take turns.
Stated another way, your ma-

chine is in one routine while
your opponent's is in another
. . . then you each switch
routines.

The other subroutine beyond
this point is a timing loop called
"wait loop" to assure both rou-
tines run in step. You can short-
en this loop when you get the
hang of interactive operation.

Digging deeper into the
"Your Turn" routine, you're
asked how many bytes you
want in line 1040. The value you
input is sent to your opponent's
computer via the cassette port
in line 1050. The line 3000 "Flag
on Play" subroutine called in
line 1060 then tests for valid
play. The other variables in the
"Your Turn" subroutine (W & L)
are simply wrong answer
counters for each turn. We exit
the routine in line 1090. But not
before we tell the computer
that it is now your opponent's
turn(Z = 2).

Going back to line 100 and
the "Take Turns" routine, the
computer now knows it is your
opponent's turn (Z = 2) and so it
branches to the "Opponent's
Turn" routine at line 2000. These
routines are essentially the

Playing interactive games over the phone lines is just one application for Mickey Modem. Businesses
can exchange data between satellite offices. And the deaf network users can get rid of their old
Teletypes.

same, except for the getting of
data from your opponent's
computer at line 2040. Notice
that Z is reset to 1 (your turn) be-
fore we exit. So your computer,
for want of better words,
zigzags back and forth from
these routines, depending on
the value of Z.

The "Referee" subroutine at
3000 tests for a valid move, then
performs the subtraction from
the stack of bytes. If an invalid
move was attempted, a branch
is made to the line 3100 routine
where both players are notified.
The wrong answer counters are
incremented, and the player is
given a second chance. If he
still "muffs it," the game is
called. The routines at line 3200
and 3300 are the "Win/Lose"
and "Game over" exiting rou-
tines.

If you've managed to stay
with the program description to
this point, you may notice that
the routines are structured so
they can be applied to nearly
any interactive program. Of
course, the rules and game-
related calculations would be
different, but the basic subrou-
tine structure and counters can
stay the same. Once the details
are worked out, it is easy to
apply your own pet games to
this program structure.

Getting Started
Is the Slowest Part!

Mickey Modem is so simple
to build that just getting the
parts together may be the
hardest part. Nothing in the cir-
cuit is critical other than the
need for adequate shielding.
For many, the data exchange
speed may be slow. But as the
old computer bromide goes, "If
it's faster than you can read
It . . . it's fast enough!" If you
find you really need more
speed, then go for the throat
and install a wide-band laser
link.

On the other hand, you can
have a ball with this arrange-
ment, especially when you pull
a super sneaky feat on your op-
ponent by modifying the soft-
ware routines in your machine
so your opponent is really play-
ing your computer alone
...and losing! Devilish, isn't
lt?B

REM
REM
REM
REM
CLS: PRINT "THIS IS THE NEAT GAME OF

5
10
15
20

25
30
35
40
45
50
55
AG
65
70
75
//
B0
05
90
95
100
105
110
120
130
1000
1010
1020
1030
1040
1045
1050
1060
1065
10/0
1030
1090
20
2010
2020
2030
2040
2045
2050
2055
2060
20/0
2030
2090
30 00
3010
3020
3030
3040
3050
3060
30/0
3080
3100
3110
3115
3120
?5

INTERACTIVE 23 BYTES
BY SO GIBSON 1/9/77

PRINT" *** 23 BYTES K**":PRINT

00sub4 : re m get names

j-o:rem set came cntr

print "now decide between you who goes first

PRINTA*;

AND

B* *

INPUT Z : IFZ>2THEN30 : IFZ<1THEN30 : IFZOINT < Z ) THEN30

CLS : PRINT "HERE ARE THE

PRINT "WE START WITH

PRINT" 1»2 OR 3 BYTES

PRINT "THE LAST BYTE.

PRINT "I'LL BE THE REPEREE AND KEE

FORN-1T01 000 JNEXTN: PRINT "OH YEE!

RULES

>3 BYTES. EACH PLAYER IN TURN CAN TAKE
FROM THE PILE. THE PLAYER THAT TAKES"
. LOSES ! " J PRINT

SCORE. NO
. ♦ ♦ FOR THOSE

THIS IS GAME *" t J

312

3130

3140
3150
3160
3200
3210
3215
3220
3230
3240
330
3305
3310
3315
3320
3330
40 00
4010
4020
4030
*050
4060
50
5010
5020

WD CHANCE

PRINT "A 'BYTE' IS WHAT RADIO SHACK GETS FROM

FORT" 1 T05 : GOSUB50 : NEXTT

REM

REM BEGIN GAME HERE

GUSUB50 : GOSUB50 : CLS

PRINT " READY ♦ . . " : X«23 : J« J+l : PRINT "

REM

REM TAKE TURNS FROM HERE

GOSUB500 0:CLS

IFZ-1 THEN10 00

IFZ«2 THEN20

REM VERY HARD TO GET PAST HERE
REM

rem your turn

w*ojl-o:rem wrong answer cntrs

print" there are now ";x»" bytes."

input "how many do you take " ; y i print "thank

LHL>1

PRINT*-! rYtREM PRINT TO OTHER PLAYER

GOSUBSOOOtREM 1ST 4 VALID PLAY

IFL-2THEN1080

IFW=HHEN1 0301 REM

Z«2

GOTO10

REM OTHERS TURN

H-0SL-0SREM WRONG ANSWER

PRINT "THERE ARE NOW

PRINT* AND NOW MB*!'

INPUT* 1 r Y J PRINTB* t "

L-L+l

GOSUBSOOOTREM 1ST 4 VALID PLAY

IFL-2THEN2070

IF W=: 1 THEN2 2 : REM 2ND CHANCE

Z«l

GOTO10

REM

REM 'FLAG ON THE PLAY TEST'

REM

IFY>XTHEN310

IFYOIN T < Y ) THEN31

IFY<1THEN310

IFY:: 3THEN310

X-X-YtREM YANK OUT BYTES

IFX" THEN32 : REM GAME OVER

RETURN

REM REFEREE SHOWS MUSCLES ♦ . ♦

tt-H+1 : CLS : PRINT " OK .... BEEP ♦ . ♦ BEEP ..... STOP THIi

PRINT: REM SKIP SPACE WHILE COMPUTER COOLS OFF

IFZ==1THENPRINTA* ?

CHEATING M ! ! "
OF YOU THAT WONDER , "
MARKET ! H "

IBM ' S

YOU.": PRINT "PLEASE STAND BY.

" iXi "

CNTRS
BYTES . "
TAKES A TURN.
JUST TOOK " ?Y?"

PLEASE STAND
BYTES ♦ "

BY.

MUSIC ! ! !

IFZ-2THENPRINTB* ;

PRINT" JUST TRIED
IFW>1THEN3300:REM
PRINT "I'M JUST AS

TO PULL A FAST ONE
REAL TROUBLE
SMART AS AN IBM

3/0 AND"

♦SO LET

PRINT" I KNOW MY BITS FROM MY BYTES.

PRINT " I ' UL GIVE YOU ANOTHER CHANCE . " : RETURN

REM WIN/LOSE

PRINT " TOO BAD ♦ ♦ ♦ " ?

IFZ- 1 THENPRIN T A* t

IFZ-2 THENPRINTB* t

PRINT" LOST THIS ONE ♦" X PRINT " BETTER LUCK NEXT TIME.

'S STICK TO THE RULES.

PRINT " OKAY . ♦ . LET ' S

PRINT" THIS GAME IS

IFZ - 1 THENPRINT A* ?

IFZ-ZTHENPRINTB**

PRINT" WONT PLAY FAIR.

FORN- 1 TOl : NEXTN I PRINT

GOSUB50 : GOSUB50 : GOTOB0

REM

REM GET PLAYER NAMF

INPUT "WHAT IS YOUR

PRINT "OKAY "?A*;"»

INPUT B*

RETURN

REM

REM THE GEE WHIZ 'LET

FORN* I. TO 1 : NEXTN : RETURN

PLAY AGAIN. " J COT 08
OVER ♦ " i

:gosub5ooo

«.»*«»*...

»»»...*

. SPOIL SPORT •

NAME
WHAT

" ?A*

IS YOUR

OPPONENT'S NAME?"

WAIT ' LOOF

Program listing.

TARBELL SOFTWARE
Extensive & Inexpensive.

TARBELL CASSETTE BASIC only $36.00

Most features of ALTAI R* Extended BASIC are inclu-
ded PLUS these added features:

• Assignment of I/O

• Alphanumeric line labels

• Unlimited length of strings

• Unlimited length of variable names

• Procedures with independent variables

• Number system 10 digits BCD integer or floating
point

Included are commands unique to TARBELL CASSETTE
BASIC which provide capabilities to:

• Initialize I/O channel •Assign a physical device to
a logical device • Drop an I/O channel previously assign-
ed • Save the BASIC interpreter and monitor or I/O
routines on cassette • Cause programs to be appended
onto programs already in memory •Call a procedure
and pass variables on the list •Cause interpreter to enter
edit mode using 15 single character edit commands.

Tarbell BASIC occupies 18K of RAM. Source is available
on cassette, CP/M** Disk, and printout-all at reasonable
prices. Price for TARBELL CASSETTE BASIC and com-
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CP/M Disk Operating Systen

The I/O section of this software has been modified
to operate with the TARBELL Floppy Disk Interface in
24K bytes of memory. Five commands permit listing of
directory, typing contents of an ASCII file, renaming
a file, erasing a file from disk, and saving memory on
disk. Fourteen programs are included which are invoked
like commands. Six source files are included for transfer-
ring between TARBELL Cassette and disk, cold-start
loading, Basic I/O system with drivers, and reformatting
crashed diskettes. Documentation includes a listing of
BIOS and instructions to patch CBIOS for your system.
Price is $100 on CP/M diskette with documentation.
(CP/M is a product of Digital Research).

Update Package

A TARBELL Update Package for those now using
CP/M 1.3 is now available on diskette. The Update
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Price: $50.00.

BASIC-E Compiler

Designed to work with CP/M Disk Operating System
this software requires a total of 20K bytes of memory.
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CBASIC Programming Syster

Upward compatible from BASIC-E, CBASIC is simi-
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file maintenance. Strings of characters may be read from
the console to permit correct input line format to be
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priced at $100. (Copyright Software Systems.)

SPOOLER

This 8080 program will save many hours of computing
time. It intercepts a\\ output to the list device, spools the
output to a high-speed disk file, and directs the spooled
data to a low-speed printer during unused cycle time while
the CPU waits for transfer of data to and from the console.
System throughput is greatly increased with the aid of
SPOOLER. Output is never lost due to insufficient memory
allocation. Fully compatible with the CP/M file system,
SPOOLER permits parallel processing without hardware
interrupt, and with minimal impact on other processes.
Price: $50.00 (Copyright KLH Systems.)

Til *ALTAIR is a trademark/tradename ofMITS, Inc.

**CP/M is a trademark/tradename of Digital Research.

( f yZJyJ&/s 95 DOVLEN PLACE • SUITE B • CARSON, CALIFORNIA 90746

(213) 538-4251 • (213) 538-2254

EMPLan 8080 APL

Especially suited to educational applications, EMPL
is an adaptation of APL, using the ASCII character set.
This 8K version occupies the first 5376 bytes of memory
and operates in two modes. The Execution Mode per-
mits all instructions to be executed immediately. The
Definition Mode permits the user to enter functions.
EMPL on Tarbell Cassette with manual is $15.00.
(Copyright 1977 Erik Mueller).

TARBELL SETS STANDARDS

For Hobbyists and Systems Developers

Sales to thousands of hobbyists over the past two years have proven the Tarbell Cassette
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TARBELL
CASSETTE INTERFACE

r — '

TARBELL FLOPPY
INTERFACE

• Plugs directly into your IMSAI or
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capacity of 256K bytes.

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• Hardware includes 4 extra IC
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• Full 6-month warranty and exten-
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• PRICE:

Kit $190 Assembled $265

DISC

Plugs directly into your IMSAI or ALT AIR •

Fastest transfer rate: 187 (standard) to 540 bytes/ second

Extremely Reliable— Phase encoded (self-clocking)

4 Extra Status Lines, 4 Extra Control Lines

37-page manual included

Device Code Selectable by DIP-switch

Capable of Generating Kansas City tapes also

No modification required on audio cassette recorder

Complete kit $120, Assembled $175, Manual $4

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CP/M with BASIC-E
and manuals: $100

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PROTOTYPE

BOARD

Model 1010

Gold plated edge pins

Takes 33 14-pin ICs or

Mix 40-pin, 18-pin, 16-pin and

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ALTAIR/IMSAI compatible

Price: $28.00

For fast, off the shelf delivery, all Tarbell Electronics products may be purchased from computer store dealers
across the country. Or write Tarbell Electronics direct for complete information.

* ALTAIR is a trademark/tradename of MITS, Inc.
CP/M is a trademark/tradename of Digital Research

T11

950 DOVLEN PLACE • SUITE B • CARSON. CALIFORNIA 90746

(213) 538-4251 •(213) 538-2254

Do It with a Kimsi!

What's this—S-100 boards with a KIM? Forethought Products makes it easy.

Rick Grossman

4007 Constellation Rd.

Lompoc CA 93436

In the realm of microproces-
sors the name of the game
seems to be expansion! An ex-
panded system allows the user
to incorporate the additional
memory required to run the
more sophisticated programs
that are available for KIM, such
as Microsoft BASIC or an
assembler.

After owning a KIM for over a
year, I finally got bit by the ex-
pansion bug. I wanted to run
BASIC and add a video display
system. The cost of the expan-
sion and the boards required
was an important factor since I
have a multitude of expensive
hobbies and I wish to remain in
the good graces of the lovely
girl to whom I am married. The
price of the motherboard and
power supply required for the
additional memory was, of

course, important. A greater
consideration was the cost of
the boards that were going to
be used to expand the system.

After reading the advertise-
ments in various magazines
and comparing prices of mem-
ory boards, I decided to go with
the S-100 bus. The popularity of
the S-100 bus will continue to
bring the prices down in the
future as more companies are
attracted to this lucrative mar-
ket. The best overall expansion
system appears to be the Kim-
si, which provides the required
interface circuitry along with
memory decoding that allows
use of KIM's 1K of on-board
memory. It also allows use of
most of the S-100 boards cur-
rently available and provides
regulation for the 5 volt and 12
volt power for KIM.

The Kimsi kit sells for $125
and goes together with relative
ease. There are no MOS or
CMOS integrated circuits that
are easily damaged by static
electricity. All of the integrated

circuits are socketed, and the
board has a solder mask on the
foil side to help prevent solder
bridges between the runs.
These factors and a complete
Instruction manual make for
easy assembly of the board.
The system was functional in
about three hours.

The Kimsi motherboard is de-
livered with one S-100 connec-
tor and has provisions for seven
more. A word of caution about
the installation of the connec-
tor: Make sure it is seated prop-
erly against the motherboard
before you solder it in place. If it
is installed incorrectly, it is all
but impossible to fix. It should
also be noted at this point that
the Kimsi board must be in-
sulated from the metal frame if
installed in a cabinet. This is
done by installing insulated ex-
truded washers on the mount-
ing screws that fasten the Kim-
si board to the case.

The Kimsi Plus power supply
is an excellent addition to the
system. Of course, a power

supply could be built to power
the S-100 system, but this unit
in kit form at $69.50 is really a
good investment. The supply is
an open frame type and is de-
signed so the physical height is
the same as the total height of
the Kimsi with the standard
S-100 board installed.

The power supply is quite
hefty, capable of supplying
+ 8 V dc at 10 Amps, + 16 volts
at 1 Amp and -16 volts at 1
Amp. The transformer is capa-
ble of 16 Amps, and the 30 Amp
rectifier delivers full power out-
put without forced-air cooling.
Previously, KIM was running on
a home-brew supply that put
out +5 volts at 2 Amps and
+ 12 volts at about 1 Amp.

I encountered considerable
difficulty getting the tape to
load and dump. Addition of the
Kimsi Plus power supply com-
pletely solved the problems.
The power supply, like the Kim-
si, is easy to build. I suggest
that when wiring the power sup-
ply connector, you use large

orctliomjlit Products

Interface Motherboard

Assembly Operating

Manual

1. Kimsi interface/motherboard kit.

2. Kimsi Plus power supply kit.

enough wire on the + 8 volt line
to handle at least 8 Amps. This
allows for additional boards to
be installed in the future.

Two methods can be used to
connect KIM to Kimsi— either
directly through two 22/44 pin
connectors, soldered back to
back, or by a ribbon cable with
22/44 connectors soldered to
each end. There are two more
connections to be made— the
decode enable signal and the
+ 12 volt supply for tape opera-
tion, which is made from the ex-
pansion connector to the appli-
cation connector on the KIM
board. I found the cleanest way
to jumper these connections
was to hard-wire pins 19 and 20
on the expansion connector to
k and n on the application con-
nector of the KIM board. I ini-
tially used a ribbon cable to
connect the KIM to Kimsi and
constructed one about ten
inches long with connectors on
each end.

When I brought up the sys-
tem and tried to run the mem-
ory/cable test program sup-
plied in Kimsi documentation,
the Vector Graphic 8K memory
board I had installed did not
pass the test. The cable was
then shortened to five inches,
and the test ran perfectly. This
was necessary because there
is no buffering in the Kimsi of
the address and data lines go-
ing to KIM. Excessive cable
length may cause crosstalk
and interfere with the data
transmission. The other prob-
lem that may occur is propaga-
tion delay.

Propagation delay will cause
the signals arriving at the CPU
to be slowed down so they do
not arrive in time for proper pro-
cessing. This problem is a func-
tion of cable length, the timing
tolerance of the CPU and the
crystal frequency tolerance in
KIM. The Kimsi instruction
manual suggests lowering the
frequency of the clock from 1
MHz to approximately 980 kHz
to alleviate the problem when
exceedingly long cables are
used. The frequency of the
clock in KIM could be changed
by using a crystal with a lower
frequency or installing an RC
network instead of the crystal
as illustrated on page 43 of the
KIM hardware manual.

The Kimsi and Kimsi Plus
power supply will provide the
flexibility of the S-100 bus com-
bined with the advantages of
the 6502 processor to make for
an excellent low-priced system.
The entire cost for this system,
which includes KIM, Kimsi,
Kimsi Plus power supply, video-
monitor, 8K memory, video
board and keyboard, is less
than $1000. This may seem to
be a little more expensive than
a PET or Radio Shack system.
However, the number and dif-
ferent types of S-100 boards
available provide a versatile
microprocessor system.

If you plan further expansion,
Kimsi and Kimsi Plus are avail-
able from:

Forethought Products

PO Box 8066

Coburg OR 97401

(503) 485-8575 ■

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The Remarkable Apple-ll

Owners of the Apple computer already know that theirs is a fine machine. This
happy Apple-ll owner has some things to say that may convince the rest of you.

In 1976, after many years of
dreaming about it, I finally
got my first personal computer.
At that time, a rather unknown
little company by the name of
Apple Computer advertised
their Apple-I system for
$666.66. It consisted of a 6502
microprocessor, 4K bytes of
RAM, power supply and all the
other necessary electronics.
But most important, it came ful-
ly assembled.

I phoned the company to in-
quire about ordering an Apple-I.
It was during this phone con-
versation that I was told of their
upcoming Apple-ll computer, a
system that would display not
only alphanumerics, but also
color and high-resolution
graphics! But this new comput-
er was not scheduled to be
marketed until around Novem-
ber 1976, so I began playing the
waiting game.

Then, around late Septem-
ber, I received word that, be-
cause of difficulties, the Apple-
il would not become available
until sometime in 1977. Tired of
waiting, I went ahead and
bought an Apple-I. Later, in the
summer of 1977, when the
Apple-ll became available, I
was able to receive a fair trade-
in allowance on my Apple-I sys-
tem towards the purchase of an
Apple-ll.

The Hardware

Probably the most impres-
sive feature of the Apple-ll com-
puter is its color-graphics capa-
bility. This graphics mode can
be operated either as a 40 x 40

element display with room at
the bottom of the TV screen for
four lines of text, or as a 40 x 48
element display with no text.
Each raster element can be set
to any one of 16 colors. Since
the color-graphics display buf-
fer coincides with the text buf-
fer (hex 0400 to about 07FF), a
system with as little memory as
4K can utilize this color-
graphics feature.

In addition to this 16-color
low-resolution graphics, the
Apple-ll also has four-color
(black, white, green and purple)
higher-resolution graphics. (It
was actually this HIRES (high
resolution) graphics capability,
not the LORES color graphics,
that prompted me to get an
Apple-ll.)

As with the lower-resolution
16-color graphics mode, the
HIRES graphics can be oper-
ated either with space for four
lines of text at the bottom of the
TV screen or with no text. Since

HIRES graphics requires al-
most 8K bytes for the display
buffer, it cannot be used effec-
tively with systems having less
than 12K bytes of memory. (Ac-
tually, 16K minimum is recom-
mended.)

In its literature Apple Com-
puter, Inc., says, ". . . Apple-ll
can generate a high-resolution
(280 H x 192 V) graphics display
in four colors. . . ." This state-
ment is somewhat misleading,
if not erroneous. It implies that
you can generate a 280 x 192
dot display in which each dot
can be set to any one of four
colors.

Actually, the computer dis-
plays 280 x 192 dots, half of
which can be either green or
black, while the other half can
be either purple or black. Thus,
on a color TV the resolution is
only 140 x 192 with four colors
per raster coordinate; on a
black-and-white TV, the resolu-
tion is 280 x 192 with only two

colors (black or white) per
raster coordinate.

The Apple-ll can, of course,
also display text without graph-
ics. In this mode it has a capac-
ity of 24 40-character lines. Text
characters can be displayed as
either normal video (white on
black), inverse video (black on
white) or flashing. And since
the display is completely under
sofware control, text can be
placed anywhere on the screen
in any order and in any video
mode. (The Apple-I, by com-
parison, only allowed for a slow
serial display of normal video
and had no graphics capability
at all.)

In addition to visual output,
the Apple-ll has a built-in
speaker, which is accessible
via software. This is useful for
producing games with sound
effects, generating computer
music, etc.

Also built onto the Apple-ll
board are eight peripheral
board connectors for interfac-
ing to the outside world, and a
game-paddle connector capa-
ble of handling up to four input
paddles. (Two paddles come
supplied with the computer
system.) The game paddles are,
of course, nothing more than
potentiometers; but the Apple-
ll's ability to read resistance
values means that you have es-
sentially four built-in A/D con-
verters at your disposal! No
other personal computer on the
market offers this feature as
part of its standard configura-
tion.

The cassette interface,

which is also built right onto
the Apple-ll board, is capable of
1500 bps. This means you can
load or save a 4K byte program
in less than 30 seconds. To load
a program from tape, connect
the line-out (or earphone) jack
from the tape recorder to the
cassette-in jack on the back of
the computer; to save a pro-
gram on tape, connect the cas-
sette-out jack on the back of
the computer to the micro-
phone jack on the recorder.
(Note that the line-in jack of the
tape recorder is not used with
the Apple computers. Many
dealers who are used to other
computers' cassette interfaces
often use the wrong jack when
recording from an Apple.)

One oversight in the design
of the cassette interface is the
failure to utilize the remote
start/stop jack found on most
portable cassette recorders.
This implementation would
have been useful for data pro-
cessing, creating and assem-
bling symbolic source code,
etc. In other words, it would be
nice to be able to read data
from an input tape, and then
stop the tape while that data is
processed.

The Apple-ll uses the new
16K dynamic RAM chips. The
board contains three rows of
memory sockets with eight
sockets per row. Thus, the com-
puter has the capacity to hold
up to 48K bytes of memory on a
single board! In addition, the
Apple-ll comes with 8K bytes of
ROM, which contains the sys-
tem monitor (2K) and Apple
BASIC (6K). Two additional
empty ROM sockets are provid-
ed for future expansion.

Apple Computer was the first
company to produce a comput-
er powered by a small, light-
weight switching power supply;
most of the other manufactur-
ers' machines have large, bulky
power supplies. Consequently,
the Apple-ll does not even re-
quire a cooling fan. In fact,
when you take the lid off an
Apple-ll and look inside, it
seems almost empty! By avoid-
ing the use of heavy compo-
nents and by packaging the
unit in a plastic case instead of
a steel case, the designers of
the Apple-ll created a truly por-

table, lightweight computer.

Apple-ll Monitor

Besides allowing you to ex-
amine and/or modify memory
locations (as you'd expect from
a monitor), the 2K ROM monitor

The cassette routines in the
monitor also utilize a check-
sum to help insure that tapes
are read back correctly. The
Apple-I firmware did not use a
checksum. (When I first pointed
out this deficiency, Apple's re-

Example of the low-resolution color-graphics mode.

also contains many other use-
ful features. One of the handi-
est routines in the monitor is
the miniassembler. It allows
you to enter an assembly-lan-
guage program from the key-
board, and assembles it line by
line as you type. You must
specify all addresses in ab-
solute hex since the minias-
sembler does not use a symbol
table.

Also built into the monitor is
a handy disassembler for con-
verting machine code back into
mini-assembly language.

To aid in debugging pro-
grams, the monitor also has the
ability to either single-step
through a program or trace the
flow of execution while the pro-
gram is running. Thus, if a pro-
gram hangs up, you can deter-
mine exactly where it is stuck.

The monitor also contains
the routines for reading and
writing cassette tapes. The tim-
ing and formatting of the tape
are done with software, not
hardware. This means that,
given the right software, it
should be possible to read or
write tapes in almost any for-
mat (Kansas City, Tarbell, etc.).
However, Apple-ll does not use
one of the standard formats
... it uses a format of its own.

ply at that time was that their
cassette interface was so reli-
able it didn't need a checksum!)

Apple-ll BASIC

The Apple BASIC interpreter
is almost legendary as one of
the fastest, if not the fastest, in-
terpretive languages on any
microcomputer. Of course, one
of the reasons for its high
speed is that it's an integer-
only BASIC. But then, there are
many applications (like games)
that do not require floating-
point operations. In fact, Apple
BASIC (which is on ROM) and
the Apple-ll itself are both
ideally suited for creating com-
puter games. The paddle con-
trols, the built-in speaker and
the exceptional graphics capa-
bility make it easy for you to
produce arcade-quality video
games.

Apple's integer BASIC turns
out to have some powerful fea-
tures, some of which are not
usually found in other BASICS.
For example, the TRACE com-
mand causes each line number
to be displayed as it is ex-
ecuted.

Another handy debugging
feature is the DSP command,
which allows you to see where
and how variables become re-

defined in your program. PEEK
and POKE commands allow ac-
cess to absolute memory loca-
tions and are useful for passing
arguments to machine-lan-
guage subroutines (which can
be invoked with the CALL com-
mand), among other things.

Not surprisingly, Apple BA-
SIC also supports the low-reso-
lution color-graphics capability
of the hardware. For example,
the PLOT command allows you
to plot points, VLIN allows you
to draw vertical lines, etc.

What is surprising is that the
HIRES graphics capability is
not supported directly. There
are no commands in the lan-
guage to do any HIRES plot-
ting. (This omission, I was told,
occurred because the HIRES
routines had not yet been com-
pleted at the time the ROMs
were made. Future versions of
Apple BASIC will support the
HIRES feature.)

Apple-ll Software

In November 1977, Apple
Computer released the float-
ing-point BASIC for their Apple-
ll systems. Written by Micro-
soft, the same company that
wrote Mits BASIC and the
BASIC for Commodore's PET
computer, Apple's new BASIC
(called Applesoft) now allows
the Apple-ll to be used for more
serious applications than just
playing games. The new BASIC
is intended for use in business,
scientific and educational ap-
plications in which decimal
numbers must be manipulated.

The Applesoft BASIC, like
the integer BASIC in ROM, also
supports the low-resolution
color-graphics capability of the
Apple-ll, while the HIRES
graphics is, again, not support-
ed. But this time the omission
is understandable since the
floating-point BASIC resides in
part of the primary HIRES dis-
play area and thus cannot be
used for graphics. (HIRES
graphics is possible with the
floating-point BASIC if your Ap-
ple-ll has at least 24K bytes of
memory. But you must call sep-
arate machine-language
subroutines.)

This HIRES graphics prob-
lem is currently being worked
on at Apple, and a new floating-

point BASIC that doesn't have
the memory conflict may soon
be coming out.

Because they are interpretive
languages, all BASICS, includ-
ing Apple's integer BASIC, are
relatively slow. Sometimes it is
necessary to produce code that
executes as quickly as possi-
ble. For these applications the
Apple-ll has, as part of the sys-
tem monitor, a miniassembler
that is very useful for writing
small machine-language pro-
grams.

What about writing large ma-
chine-language programs?
Yes, you can also use the mini-
assembler to produce big pro-
grams (it's a lot better than as-
sembling them by hand!). But
the main problem with a mini-
assembler (not just Apple's) oc-
curs when you have to insert
new code in the middle of an al-
ready existing program. Your
only resort is to patch in the
changes (i.e., insert a JUMP in-
struction to some other part of
memory containing the needed
code, and then return). This
tends to produce confusing
program flow.

Assemblers are usually writ-
ten for microcomputers with
source code read from one in-
put tape and object code writ-
ten onto another output tape.
But the Apple-ll only supports
one cassette unit, which can-
not be started or stopped under
software control.

To get around this problem, it

Example of the high-resolution graphics mode.

is necessary to store the
source code and/or object code
in memory, along with the
assembler itself. This approach
has actually been used; text
editors/assemblers for the
Apple-ll are currently available
from several sources. (I have
recently modified Microsoft-
ware Specialists' ASSM/TED
program for the KIM to run on
the Apple-ll. Copies of this
modified program are available
from: Microproducts, Hermosa
Beach CA, (213) 374-1673.)

As more and more Apples get
around, more and more Apple
software will appear, especially
games and applications soft-
ware. Apple has started a new
service called the Apple Soft-
ware Bank from which Apple
owners can receive document-
ed and tested software. And if

you've written a worthwhile
program, you can submit it to
the Bank for others to use.

Apple-ll vs the Competition

The Apple-ll computer comes
completely assembled in an at-
tractive plastic case with a full
ASCII keyboard. A vinyl carry-
ing case is also supplied with
the unit for ease of portability.
Since the machine is easy for
almost anyone to set up and
use, the Apple-ll just might be-
come the leading "appliance"
computer of the future.

The original price of an Ap-
ple-ll, complete with 4K bytes
of RAM, was around $1300. In
the early days of personal com-
puting, a system like the Apple-
ll at this price would have been
a fantastic bargain. For many
years B.C. (Before Commo-

dore), computer kits with much
less capability than the Apple-ll
were selling for much more
money.

But as we enter the era of
cheap computing, the pricing
standards of yesterday are be-
coming obsolete. At least two
companies (Commodore and
Radio Shack) are each offering
completely assembled 4K ap-
pliance computers for about
$600. Although this price in-
cludes both a cassette tape
recorder and black-and-white
TV display, neither system of-
fers color or high-resolution
graphics (however, Radio
Shack says they plan to offer a
similar capability sometime
this year at an additional cost).

Furthermore, both compa-
nies seem to be having prob-
lems in actually delivering their
machines— each is quoting a
three-to-four-month waiting
period. But you can get an
Apple-ll right now; and with it
you'll get a good set of useful
documentation.

In early 1978, the price of a
4K Apple-ll was lowered to
$995. Although this is still a lit-
tle higher than the price of a
PET, you get a lot more com-
puter for your money. I bought
my Apple-ll (serial number
0013) at the higher original
price, but I've never regretted it.
Now that the price has been
lowered to below $1000, there's
no excuse for not getting an Ap-
ple-ll of your own!!

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"Texas residents must include an
additional 5% for factory orders. MC &
Visa cards honored.

PERCOM™ peripherals for personal computing'

PEFQCM

PERCOM DATA COMPANY, INC.

DEPT. K
318 BARNES • GARLAND, TEXAS 75042

Phone:(214)272-3421

Universal Number Converter

This program makes a dandy hex-decimal-octal-binary converter, but that's not all.
It can also serve as a fine device for teaching people about other number bases.

E as ton Beymer
PO Box 2821
Huntsville TX 77341

While in the process of
writing a cross-assem-
bler for the MO S Technology
6502 processor, I found it
necessary to design a routine
for the conversion of decimal,
octal and binary numbers
into hexadecimal notation.
After studying the problem, I
noted that a common routine
could be written for con-
verting numbers in all three
bases into hexadecimal.

The program in this
article, written in Com-
modore PET BASIC, is an
outgrowth of my efforts in
providing the desired com-
monality in my cross-assem-
bler. In addition, it includes
the capability of converting
any number of base 2 to base
16 to any other base-2-to-16
number. The upper limit as to
the size of the number that
can be converted is strictly a
function of the number size
allowed by the BASIC inter-
preter used. In the case of the
PET, it is limited to
999,999,999, or the number
of characters input before the
automatic line feed/carriage
return occurs.

Although there seems to
be little use in converting a
base-5 number to base 13, for
example, the capability is
there as an outgrowth of the
design. However, the unre-
stricted movement between
octal, decimal, hexadecimal
and binary should be useful
to anyone working on a
machine-language or assem-
bly-language level.

The program can be used
as a stand-alone routine for
general purpose use or as a
teaching tool to show the
relationships between the

different number bases. Also,
the driver or mainline portion
of the program can be dis-
carded, and the base conver-
sion subroutine used in appli-

cations such as disassemblers,
cross-assemblers, and memory
dump routines where pro-
cessing speed is not particu-
larly important. ■

100 RE* * 5ASE CONVERSION ROUTINE *

110 RE* WRITTEN BY EASTDN BEYMER

150 PRINT

200 INPUT "INPUT eASE"; B IX

210 IF BI*<2 OR BISM6 THEN 6CG

220 INPUT "INPUT NUMBER"; NIS

300 INPUT "OUTPUT BASE"; BO*

310 IF B0*<2 OR B0S>16 THEN 6C0

400 G0SUB 10000

410 PRINT "OUTPUT NUM8ER="; N0S

500 GO TO 150

600 PRINT "BASE NOT IN RANGE";

610 PRINT " OF 2 TO 16"

700 GO TO 150

iCCOC REM BASE CONVERSION SUBROUTINE

10100 RFM CCNVERT TO DECIMAL

10150 LT=LEN(NI$)

10200 OEC=0

103C0 PWP%=0

10400 FOR J = L? TO 1 STEP -1

105C0 K*=ASC(MID*(NI$ f Jtl) »

10700 IF K%>64 THEN K«=K%-7

108J0 K3=K*-48

10810 IF K*<BI% AN0 K%>-1 THEN 10900

1C820 PRINT "INVALID INPUT FOR BASE";

10830 PRINT BI^

1C840 N0S="????"

10650 RETURN

10900 DEC=DEC*K**BI*t PWR*

11C00 PWR*=PWRX*1

11100 NEXT J

11110 REM CONVERT DECIMAL TO eASE #

11120 H$="0123456789ABCDEF"

11130 NC*=""

11200 PWRX=L0G(DEC)/L0GCB0%)

11300 FCP J=PWR% TO STEP -1

11310 XX^INT(BOttJ)

11320 CH*=DEC/XX

11500 N0$=N0S*MID$( H$,CH%«-1, II

11600 DEC=INT(DEC-CH**XX)

11700 NEXT J

11800 RETURN

11900 END

Program listing.

INPUT BASE? 16
INPUT NUMBER? FFFF
OUTPUT BASE? 10
OUTPUT NUMBER=65535

INPUT BASE? 10
INPUT NUMRER? 65535
OUTPUT eASE? 8
OUTPUT NUMBER=177777

INPUT BASE? 8

INPUT NUMBER? 177777

OUTPUT BASE? 2

OUTPUT NUMBER-llilllililiiilli

INPUT BASE? 5
INPUT NUMBER? 345
OUTPUT eASE? 13
INVALID INPUT FOR BASE 5
OUTPUT NUMBER*????

INPUT f?ASE? 5
INPUT NUMBER? 344
OUTPUT EASE? 13
OUTPUT NUMBER=78

INPUT BASE? 13
INPUT NUMBER? 78
OUTPUT BASE? 5
OUTPUT NUMBEP=344

INPUT BASE?
BASE NOT IN

RANGE OF

2 TO 16

INPUT eASE? 16

INPUT NUMBER? ABCD

OUTPUT BASE? 2

OUTPUT NUMBER=1010 101111001 101

INPUT eASE? 2

INPUT NUMBER? 101 C 101 1 1 1001 10 1

OUTPUT BASE? 8

OUTPUT NUMBER?125715

INPUT BASE? 8
INPUT NUMBER? 125715
OUTPUT EASE? 10
OUTPUT NUMBER*43981

INPUT BASE? 10
INPUT NUMBER? 43981
OUTPUT BASE? 16
OUTPUT NUMBER=ABCD

Sample run.

Cal R. Rasmussen

175 8th St.

Idaho Falls ID 83401

Hexadecimal

Memory Dump

One good article generates another. This is a nice companion to one of last year's.

Kudos to Mark Borger-
son. His 6800 assembly-
language program for fast
loading machine-language

programs as it appeared in the
February 1977 issue of Kilo-
baud ("Cut 6800 Program-
ming Time with this Extraor-

Program listing.

dinary Program/' p. 104)
works extremely well. I re-
assembled that program to
relocate it to a convenient

00001

NAM HEXDUMP

00002

• «

00003

• HEXADECIMAL MEMORY DUMP PROGRAM

00004

»♦

00005

* LOAD VIA MIKBUG "L" COMMAND

00006

• USE MIKBUG "G" COMMAND TO START

00007

• •

00008

* ENTER ADDRESS OF FIRST BYTE TO DUMP

00009

«•

00010

• ENTER ADDRESS OF LAST BYTE TO DUMP

00011

00012

• PUSH "RESET" ON COMPUTER TO ABORT

00013

* CONTROL RETURNS TO MIKBUG

00014

• •

00015

OPT NOG

00016

OPT S

00017

OPT

00019

• MIKBUG ROUTINES USED

00020

E1D1

OUTEEE EQU SE1D1

00021

E0BF

0UT2H EQU SE0BF

00022

£04 7

BADDR EQU SE047

00023

E0CC

OUTS EQU SE0CC

00024

E0C8

0UT4HS EQU SE0C8

00025

E0E3

MONIT EQU SE0E3

00027

• START PROGRAM

00028

3F20

ORG S3F20

00029

3F20

0002

TEMP RMB 2 TEMP STORAGE FOR X REG.

00030

3F22

0002

LSTBYT RMB 2 ADDRESS OF LAST BYTE TO DUMP

00031

3F24

000 1

COUNT RMB 1 COLUMN COUNTER

location in my memory.

After implementing the
loader program, it appeared
that a hexadecimal dump pro-
gram would be a very useful
companion program. The
MIKBUG P command can be
used for that purpose; how-
ever, it has two disadvantages.
First, it is necessary to use
the M command to enter the
starting and ending addresses
at A002-A004. The second,
and more serious, disadvan-
tage is that the output is
formatted for the MIKBUG
tape punch and is very diffi-
cult to read since there is no
spacing between bytes.

Here is a program that
overcomes those disadvan-
tages. The display format is
not new, by any means, but
the only program I have seen
for this format is written to
run on an Altair 680b by
Mits. Since Mits does not use
MIKBUG, the program will
not run on my SWTP 6800
system. My program will run

on any 6800 system using
MIKBUG, or one of the
newer replacements for
MIKBUG.

I have used the same basic
dump technique as in the
Altair program, but with
input/output routines modi-
fied for MIKBUG. I have
added some prompt messages
at the beginning and have
used Mr. Borgerson's tech-
nique of relocating the stack
pointer to restart the program
by simply typing G on the

terminal.

To use the program after
loading, set the program
counter at A048-A049 to
3F25 (or the appropriate
starting address if you have
relocated the program) and
use the MIKBUG G command
to start execution. The pro-
gram title will be printed,
followed by a prompt mes-
sage, FIRST BYTE TO
PRINT. The address of the
first byte to dump is entered
and the computer responds
with LAST BYTE TO
PRINT. The address of the
last byte is entered and the
dump begins. The display
format consists of 16 bytes
per line with the address of
the first byte being printed at
the left (see Fig. 1).

There is no limit to the
amount of memory that can
be dumped at one time; any
number of bytes from one to
65K can be dumped. (Hope
you have a lot of paper for
the larger numbers!) A word
of caution: The address of
the first byte to be dumped
must be less than that of the
last. If this is not the case, all
memory locations except the
region between the two ad-
dresses will be dumped! If
both addresses are the same,
only one byte will be dis-
played.

The dump shown in Fig. 1
is a dump of the dump pro-
gram itself. This should prove
to be a valuable debugging
program; especially if your
program has "gone to that
never-never land known only
to CPUs and covered its
tracks in the process," to
quote another Kilobaud
author. ■

00032

00033

00034

00035

00036

00037

00038

00039

00040

00041

00042

00043

00044

00045

00046

00047

00048

00049

00050

00051

00052

00053

00054

00055

00056

00057

00058

00059

00060

00061

00062

00063

00064

00065

00066

00067

00068

00069

00070

00071

00072

00073

00074

00075

00076

00077

00078

00079

00080

00081

00082

00083
00084
00085
00086
00087
00088
00089
00090
00091
00092
00093

3F25

3F28

3F2B

3F2D

3F2F

3F30

3F32

3F35

3F36

3F38

3F3A

3F3D

3F3F

3F42

3F44

3F4 7

3F4A

3F4D

3F4F

3F50

3F52

3F5 5

3F56

3F5 8

3F5A

3F5D

3F60

3F6 3

3F65

3F6 7

3F68

3F6A

3F6D

3F6E

3F70

3F72

3F73

3F76

3F79

3F7B

3F7E

3F80

3F83

3F85

3F88

3F8B

3F8E

3F91

3F94

3F97

3F99

3F9C
3F9E
3FA1
3FA4
3FA6
3FA8
3FAB
3FAE
3FB0
3FB3
3FB6

1 1

A0 60
3FB7
00
2E

06
E1D1

E1D1

3FCF

06
E1D1

3F20

E0CC

3FE3

06
E1D1

F3
39

3F22

3F20

E1D1

E1DI

3F24

3F20

E0C8

3F20

3F24

E0CC

E0BF

3F22

E0E3

E0CC

E1D1

E0 47

GO
AA

ADRS1

GET

ADRS2

CRLF

NXTBYT

JMONIT
GET ADR

00095 3FB7 48

00096 3FCF 46

00097 3FE3 4C

TITLE
FIRST
LAST

00099 A048

00100 A048

00101

OUTEEE

E1D1

0UT2H

E0BF

BADDR

E047

OUTS

E0CC

0UT4HS

E0C8

MONIT

E0E3

TEMP

3F20

LSTBYT

3F22

COUNT

3F24

3F25

3F2B

ADRS1

3F38

3F4D

GET

3F58

3F63

ADRS2

3F70

CRLF

3F79

NXTBYT

3F94

JMONIT

3FA8

GET ADR

3FAB

TITLE

3FB7

FIRST

3FCF

LAST

3FE3

3F20

LDS

LDX

LDA

CBA

BEQ

JSR

INX

BRA

LDA

JSR

LDA

JSR

LDA

JSR

LDX

LDA

CBA

BEQ

JSR

INX

BRA

BSR

STX

JSR

LDX

LDA

CBA

BEQ

JSR

INX

BRA

BSR

INX

STX

LDX

LDA

JSR

LDA

JSR

LDA

STA

STX

LDX

JSR

LDX

DEC

BEQ

JSR

LDA

JSR

CPX

BEQ

BRA

JMP

JSR

LDA

JSR

RTS

FCC
FCC
FCC

ORG
FOB
END

#SA060
#TITLE
00, X
#•.

ADRS1
OUTEEE

#$0D

OUTEEE

#S0A

OUTEEE

#S00

OUTEEE

#FIRST

00, X

GET
OUTEEE

GET ADR

TEMP

OUTS

#LAST

00, X

#••

ADRS2
OUTEEE

GET ADR

LSTBYT

TEMP

#$0D

OUTEEE

#S0A

OUTEEE

#17

COUNT

TEMP

#TEMP

0UT4HS

TEMP

COUNT

CRLF

OUTS

0UT2H

LSTBYT

JMONIT

NXTBYT

MONIT

OUTS

#•?

OUTEEE

BADDR

RELOCATE STACK POINTER
POINT TO 'TITLE' MESS.
GET CHARACTER TO PRINT
PUT ASCII PERIOD IN B
IS CHAR. IN A-REG A PERIOD?

PRINT CHAR IN A REG

LOOP FOR MORE
CARRIAGE RETURN

LINE FEED

ASCII NULL

POINT TO 'FIRST* MESS.

GET CHAR TO PRINT

IS CHAR IN A-REG A PERIOD?

PRINT CHAR IN A REG

LOOP FOR MORE

GET FIRST ADDRESS

STORE IT

POINT TO 'LAST* MESS.
GET CHARACTER TO PRINT
ASCII PERIOD IN B-REG
IS CHAR IN A-REG A PERIOD?

PRINT CHAR IN A REG

LOOP FOR MORE

GET LAST ADR

ADJUST IT

STORE IT

POINT TO FIRST BYTE

SEND CR,LF

INIT COUNTER
STORE X REG

PRINT ADDRESS
RESTORE XREG

SEND A SPACE

BYTE TO A

PRINT IT, A INCREMENT X-REG

ARE WE DONE?

YES, RETURN TO MIKBUG

SEND SPACE

SEND QUESTION MARK

GET ADDRESS
RETURN

/HEXADECIMAL MEMORY DUMP./
/FIRST BYTE TO PRINT./
/LAST BYTE TO PRINT./

SA048
S3F20

STARTING ADDRESS IN PROG CTR

TOTAL ERRORS 00000

•G HEXADECIMAL

MEMORY DUMP

FIRST

BYTE TO PRINT ?3F20 LAST BYTE

?3FF5

3F20

1 1

3F30

3F4

1 1

3F5

3F60

1 1

3F70

3F80

3F90

3FA0

3FB0

3FC0

3FD0

3FE0

3FF0

•

Fig. 1

. Dump

of the dump.

Douglas A. Schwab
1591 Gerald Ave.
Glendale Heights IL 60137

IC Testing:
A Complete System

Here's a valuable addition to any home-brewer/experimenter's test-equipment collection.

How often have you found
that the "prime" in-
tegrated circuit you so con-
fidently soldered onto your
printed-circuit board was bad?
Most of us have had this prob-
lem from time to time.

In most cases, this frus-
trating experience could be
avoided by testing the in-
tegrated circuits before using
them. But the commercial IC
testers cost many thousands of
dollars. Do you simply have to

8 BITS

I6-BIT
LATCH

}

16 BITS

INTERFACE
CIRCUIT
(X 16)

16 BITS

TEST

SOCKET

CONTROL

POWER
SELEC-
TOR
SWITCH

I/O BUS
DATA LINE

Fig. 1. IC tester block diagram.

I/6 8097

READ ENABLE
I/4 7495

Vcc
6

WRITE
STROBE

I/4 74 03

IOK

Vcc

»PX

TYPICAL PIN OF
IC TEST SOCKET

OPEN COLLECTOR OUTPUT

Vx
ENABLE THIS PIN
(USED WITH POWER
SUPPLY)

"grin and bear it?" No! . . . if
you own even a modest micro-
computer system, you already
have most of what is needed to
test the little devils.

This article describes a low-
cost interface that I designed
and built for my SWTP 6800
system to do just that. All that
is required is the SWTP 6800
system with its terminal, as lit-
tle as 2K of memory and the IC
tester interface. You should be
able to duplicate the interface
with all new parts for about $50.
You won't be able to test the
gate delay of an ECL IC, but you
will be able to instantly locate
most static faults in TTL and

DTL ICs.

I wanted to keep the cost and
hardware complexity to a min-
imum. The interface is de-
signed to connect directly to
the SWTP 6800 I/O bus. Quite
simply, the IC tester interface
allows the microcomputer to
output logic conditions to the
IC being tested and examine its
response. With the proper pro-
gram logic, most gates and
clocked devices can be tested.

I chose to limit the size of the
IC to be tested to 16 pins or less
for my prototype. This number
was especially attractive be-
cause it fit on a single I/O bus
prototype PC board. Most of

Fig. 2. Pin interface circuit.

IC tester control head.

NOTE: BE SURE THAT
BOTH CONNECTIONS ARE MADE FOR
EACH Vcc CONNECTION.

VI4

P\A

•

POLE I

POLE 2
Vcc

POLE 3

10Q

Fig. 3. Power-supply connec-
tions for IC test socket.

the ICs I wanted to test were 16
pins or less, anyhow. In any
case, the basic design can eas-
ily be expanded to 32 pins, and,
with slightly more trouble, to
almost any reasonable size.

Hardware

Fig. 1. shows the general
structure of the IC tester. When
data is output to the device, it is
latched into the 16-bit data
latch. The pin interface circuit
causes the data to be applied,
bit by bit, as logic levels to the
IC under test. It also allows
logic levels to be read back into
the CPU. The logic levels are
read and written eight bits at a
time, but if U\e driving program
is properly structured, this
should not be a problem.

The real heart of this IC
tester is the pin interface cir-
cuit, which is shown in Fig. 2.
This circuit is compatible with
DTL, as well as with the popular
TTL families (74, 74L, 74S, 74LS,
74H) and standard, open collec-
tor or three-state outputs. The
typical pin can be an input, out-

IC TI

TWE

SEL res §1

m TEST

SWCE Tfl TESt
IC TYPE HUHBO 7

IC tester interface. (AH photos by Diana L. Schwab)

put, Vcc or ground connection.
The circuit also protects the
tester from damage due to
either programming or operator
error.

When a pin is used as an in-
put, the desired logic condition
is simply defined. Output pins
should be defined as logical
one. Vcc and ground should be
defined as logical one and zero,
respectively. Pin 1 is always the
most significant bit, and pin 16
is the least significant bit of the
two-byte constant. Because of
an inversion inherent to the pin

interface circuit, all data
should be ones complemented
before being output to the
device.

Fig. 3 shows the details of
the power supply for the IC be-
ing tested. A three-pole, multi-
position, nonshorting switch is
used to make the power con-
nections. Poles 1 and 3 are
grounded, and pole 2 is con-
nected to Vcc through a 10
Ohm resistor. Each switch posi-
tion corresponds to a ground-
Vcc connection pair (e.g., 7-14).
For each position, the pole-1
contact is connected directly to
the test IC pin to be grounded.
The pole-2 contact is connect-
ed directly to the pin on which
Vcc is to be supplied.

It is essential that, for each
connection made to the pole-2
contacts, the corresponding

connection be made between
the pole-3 contact and the Vx
enable for the test pin. This pro-
tects the tester against trying
to ground a pin connected to
Vcc. Fig. 4 is a complete tabula-
tion of the switch connections.
The one remaining part of the
hardware is the command de-
coder. This consists of a single
74S138 and a couple of in-
verters which provide the clock
and enable signals required by
the latches and three-state
drivers. Decoding is provided to
support 16 additional pins, if re-
quired. The "big picture/ 1 the
IC-tester detailed logic
diagram, is shown in Fig. 5.

Software Description

I have also written a program
to drive the IC tester to test
several members of the TTL

Switch

Pole 1

Pole 2

Pole 3

Position

Gnd-Vcc

Contact

7-14

P14

V14

8-16

P16

V16

4-8

11-4

P11

13-5

P13

12-5

P12

Typical operating sequence.

Fig. 4. Connections for the ground-Vcc switch.

family. It is a simple program
with many possible enhance-
ments. A complete listing is
provided in Program A. The pro-
gram is 1 table-driven, so it is
very easy to add new ICs to the
list of those that can be tested.
Each IC the tester knows
how to test is entered in the
catalog. Each catalog entry
consists of the eight-character
ASCII name of the IC, left-
justified and filled with blanks

(e.g., 7400 ). The next

two bytes contain the address
of the truth table used to direct
the test. Each entry must be ex-
actly ten bytes, and additional
catalog entries may be added
immediately before the CATOB
label.

The truth tables may vary in
length depending on the com-
plexity of the IC being tested.
The first byte must always
specify the algorithm number.

This indicates which test pro-
cedure should be used (more on
this later). The second byte con-
tains the power-switch position
number. The third and fourth
bytes contain the 16-bit count
of the number of bytes in the re-
mainder of the table.

The remaining bytes in the
table contain test data used by
the test algorithm; the formats
may vary. Three such algo-
rithms are currently defined.

(MSB) D7
D6
D5
D4

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NOTE: IC'S 1.2,3 a 5 Vcc - PIN 16,
ol GND-PIN 8. ALL OTHERS Vcc -

PIN 14, GND-PIN 7
RB

Fig. 5. IC tester — detailed logic diagram.

Algorithm one can be used to
test most gates and combina-
tional logic blocks (multi-
plexers, BCD-to-seven-segment
decoders, etc.). The test data
for this algorithm is in the
following format: two bytes of
the desired logic state defini-
tions and two bytes of the prop-
er response. Additional entries
are made as required.

Algorithm two can be used to
test edge-sensitive devices.
These include many flip-flops,
shift registers, counters and
similar devices. The test data
format is two bytes stating
definition, two bytes with ones
at pins where edge should oc-
cur and two bytes of the proper
response. Similar entries are
repeated as required.

Algorithm three tests pulse-
sensitive devices, such as
latches and memories. It is the
same as algorithm two except
that after the edges occur the
bits are returned to their
original conditions.

So far I have found no easy
way to define the truth tables; I
have simply drawn the logic
elements at the top of a page
and filled in ones and zeros in
columns below them. There has
to be a better way. I hope some-
one will write some sort of com-
piler or interpreter that will
allow the IC to be described in
terms of logical function, and
drive the actual test.

Don't forget that some short-
cuts are possible without dras-
tically degrading the quality of
the test. For instance, all four
gates in a 7400 may be tested at
the same time. Also, as long as
each input pin is tried both high
and low, all possible combina-
tions of input pins do not
necessarily need to be tried on
complex gates and enable cir-
cuits.

Operating Considerations

Operating the IC tester is ac-
tually very straightforward.

1. When the system prompts
with "Enter type number?"
enter the IC-type number
followed by a carriage return.
(Control will back-space one
character, while Control X will
delete the entire entry.)

2. Set the power-selector
switch to the indicated position

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and place the IC to be tested in
the proper test socket. Type a
space to start the test.

3. Read the test results.

4. Additional ICs of the same
type may be tested by placing
them in the test socket and
typing a space. To change to
another type, type carriage
return and proceed as above.

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tions are in order. The Vcc-
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connections should ever be
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Conclusion

So there it is . . . the IC
tester! For a small investment
of time and money, you can
have a useful and versatile test
instrument. And, best of all,
when someone gestures at
your pride and joy and asks,
"But what can it really do?"
you can show him!B

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8888

FLEXIBLE DISK SYSTEM FOR KIM-1
HDE Model DM 816-DI- 1

FEATURES:

Line numbered text entry and editing

Powerful command structure

Capability for user defined commands

Completely compatible with KIM input/output routines

Multiple resident files

Indexed storage and scratch pad

o r*

s ;

INCLUDES:

Sykes 7000 single drive disk and controller (expandable)

Power supply rated for 4 drives

KIM-4 motherboard interface card

All interconnecting cables

File oriented disk system (FODS)

User manual

90 day parts and labor warranty

THE FILE ORIENTED DISK SYSTEM:

Single or dual drive versions

Requires less than 4K bytes (F100 to FFF7)

Compatible with Microsoft K\MA BASIC and Aresco ASSEMBLER

Text editor functions/commands include:

- APPEND, END, EDIT(line), FILE(designation),

- LIST, SIZE, LOCATE, MOVE,

- PRINT, RESEQUENCE, SUBSTITUTE, NUMBERS
Disk functions/commands include:

- DELETE, DIRECTORY, LOAD,

- SCRATCH PAD(A and B), SAVE
Support functions/commands include:

- ADDRESSdine number), ASSEMBLE, CONTINUE ASSEMBLY,

- JOB, RUN, I/O SELECTION,

- JUMPfto monitor), PROMPT(change), etc.
Limited software warranty

*» * -*

PRICE: $1,995.00 F.O.B. Medina, Ohio
ORDER THE HDE DISK S YS TEM FROM

COMPUTER

P.O. BOX 523
MEDINA, OHIO 44256

(216) 725-4560

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Everything you always wanted

to plug into your PET,

APPLE or TRS-80*

HARDWARE

PRINTERS

Centronics 150 Ipm, of 20, 40
or 80 char. (Upper/lower case).
PI Parallel Model (cable, soft-
ware, add $50) $395.

SI Serial Model (cable, soft-
ware add $50) $549.

Anderson- Jacobsen I/O Selectric,

Bidirectional $995.

PET Graphics Ball . . . $200.

RS 232C Serial Option. $200.

TRS Graphics Ball . . . $100.

Expandor 123P impact with

tractor feed $495.

Integral Data IP-125 impact

Upper/lower case $795.

PET, TRS-80 graphics option
with 4 char, sizes, tractor feed
$1195, Pet Modem, $320, Ser-
ial Int. $98, (Apple $62),

Apple Modem $120

MEMORY (Save $100 or more)
16K Dynamic RAM (TRS-80
Specify keybd. or exp. int.$200j
16K RAM Board, options$435

Additional 8 K $200

CONNECTORS, ETC.
TRS-80 40 oin edge. $9.95.
Int. ext. cord, $19.95+$2*(Ft-2)
IEEE or User Port w/cover $9.95

Cassette w/cover $4.95

i Dual Stereo Cassette Deck Ideal

for micro tapes w/prompting$250.
i C-10 Blank cassettes . . . $1.49

SOFTWARE

f*hnt uiprp afraid vnn rniilrln't affnrri) 1TRS-80:| 1. Data Management/ Report Gen-

\ out were arram yoi ) uian lan ora; 1 erator p' aC kaae (L-11-16K). Tape system:

ufei

I* r*i

1 3 H

MA |.

Exclusive JOYSTICK package (shown with PET
MICROCHESS). Uses Fairchild's unique 8-way joy-
sticks for true user interaction. Perfect for screen
cursor control in games, education and text editing.
PET 1 -Joystick Kit with Maze & Breakout: $39.95
Extra Joystick Kit with Two Player Game: $19.95
Assembled Add $10/ Joystick. TRS-80/Apple II Kits avail.

Call or write for free brochure rnicrOtrOnJX

Mby

age
$200; Disk System: $300. Give your
TRS-80 the editing features of a
$4000+ Bu Trough's TD800 series ter-
minal. Automatic data entry and cus-
tom reports. Generate complete
screen graphics with full cursor con-
trol. 2. MICROCHESS (LI or II-4K)
$19.95. 3 difficulty levels. 3. State-
ment ren umbering and cross reference.
IPET: J 1. Joystick Microchess-
(needs dual joystick package) $19.95
Play against an opponent while your
PET checks and saves moves. Options:
Play by phone, play against your PET.
2. Astrology:$ 14.95. 3. Statement re-
numbering and cross reference:$9.95.
lAPPLE 1171 1, 3 Dimensional Maze (16K)
$14.95. 2. Hi-Res Graphics
Editor (16K) $17.95
3. Statement renum-
bering $9.95 (8K)

TOLL FREE

MICROLINE for:
Orders, TRS-80
Tech. Newsletter
Info, free catalogue

80d-523455(f
In PA & CAN
(215)665-1112

Cash prices shown. Major credit cards accepted.
Minlmun shipping $2.50. Pa. residents add 6%.

Post Office Box Q, Dept. K, Philadelphia, PA 19105

Turn your TRS-80 into

a complete word processing system.

Just hook up the cables and connectors supplied
with your SELECTRA-TERM and you're ready to run.
Input your text and type the single command: LPRINT.
The SELECTRA-TERM automatically outputs clear,
clean high fidelity copy.

Incredibly simple!

Brand new. $1925"&
Fully assembled and tested.
Delivery five weeks.
Many options available.

*1 15 VAC, 60 Hz Model.

COMPARE THIS

DOT MATRIX OUTPUT

with the

SELECTRA-TERM high
fidelity impact
print!

Direct international sales inquiries to

International Sales Division

17648 ma Drive

Granada Hills, CA 91344 USA

Discounts Available to
EDUCATIONAL ACCOUNTS

Contact Dolores Sun

P. 0. Box 8394 • Ann Arbor, Ml 48105
(313)665-8514

SELECTRA-TERM can also be connected
to the parallel port of PET ■ Apple II ■
Heath H8 ■ IMSAI ■ Cromemco ■ Alpha
Microsystems ■ Space Byte ■ North Star
Horizon ■ SWTP ■ Vector Graphic ■ Sol ■
Polymorphic ■ Digital Group ■ Ohio
Scientific ■ Altair ■ Sorcerer ■ Xitan ■
Rex ■ KIM ■ Versatile CRT ■ EXORcisor

M30

micro

computer

devices

inc.

960 E. Orangethorpe, Bldg. F

Anaheim, California 92801

Telephone (714) 992-2270

*TRS-80 is a product of Radio Shack

4 'Innovators to the Microcomputer Industry"

Music, Music
and More Music

Software Technology Corporation has a package for all you music lovers. Music is
called the "universal language"; this lets you make music in a high-level language.

Rod Hallen
Road Runner Ranch
PO Box 73
Tombstone AZ 85638

Order a personal computer
product by mail and re-
ceive it in seven days? . . . com-
pletely assemble an S-100
music board in three and a half
minutes, or 35 minutes from
sealed package to computer
music?

Impossible? No, not if the
company is Software Technol-
ogy and the product is their
"Music System."

I have always been interest-

ed in music and, although my
piano teacher of 30 years ago
might not agree, I have always
wanted to play a musical instru-
ment. Until recently I confined
my playing to our family organ
— only when the family wasn't
at home. Because of my inter-
est I have devoured every com-
puter-music article I could find
. . . but never got around to put-
ting together the necessary
hardware.

Therefore, I couldn't quite be-
lieve or resist the brochure that
I received in the mail from Soft-
ware Technology. (Some kind
of cousin to Processor Tech-

NEW Start new file

FILE Define file size and display

LIST Display current file

DELETE Delete line or lines of file

SCORE Compile file

PLAY Play file

RETURN Return to resident operating system

Table 1. Music operating system commands. By specifying an ad-
dress or line number after a command, specific functions are con-
trolled. Only the first letter of a command must be entered — the
rest are optional.

nology, I think.) They are offer-
ing for immediate delivery—
now that's a most unusual way
of doing business— a complete
"Music System": S-100 board
kit, cassette tape with music
operating system and manual
for $24.50. Being a trusting
individual, I sent my check in
the mail the very same day; I
received my "Music System"

seven days later.

After recovering from that
surprise, I rushed home, tore
open the package and set to
work. Almost before I started
assembly I was finished!...
three and a half minutes by the
clock. This is not too hard to
understand if you consider that
the S-100 circuit board is one
and a half inches wide by six

w =

Whole note

• ^ mm

Triplet

H =

Half note

$ =

Rest

Q =

Quarter note

K =

Key

l =

Eighth note

N =

Tempo

S =

Sixteenth note

* __

Treble clef

T =

Thirty-second note

@ =

Bass clef

X =

Sixty-fourth note

P =

Part

, =

dotted note

R =

Repeat

M =

Measure

Short articulation

# =

Sharp

i»

Long articulation

& =

Flat

» ~ ~

Staccato

% =

Natural

/ =

Remark

1-2-3-4-5-6-7-8-9-A-B-C-D-E-andF
are the coding for the notes plus or minus middle C

Table 2. Music system high-level language. You can get an idea of
how it is used by comparing the coded portion of Fig. 1 with the
music. The placement of the notes on the staff is numbered in hex
plus or minus from middle C, which is zero (0). C above middle C
would be + 7. See Fig. 1, measure 5.

inches long and holds three
resistors and two capacitors.

Now, if you are sitting there
looking at your five by ten inch
S-100 boards and trying to
figure out what I'm talking
about, let me explain. This
board makes two connections
to the S-100 bus. One is ground
(Pin 50) and the other is PINTE
(Pin 28). That's all! The board is
just as long as the S-100
socket, and when inserted
makes contact with the two
pins mentioned above. Trying
to install this in a fully loaded
motherboard could be a chore. I
might even hard-wire this to my
CPU board to free a slot.

A coax cable (not included)
connects the music board to
your amplifier (necessary to in-
crease the very low signal
level), and music results. PINTE
is the 8080 Interrupt Enable
lead, and the processor manip-
ulates it in such a way that
square-wave tones are gen-
erated.

The manual (40 information-
packed pages) was obviously
written by someone knowl-
edgeable about both comput-
ers and music and how to com-
bine the two. Everything is pre-
sented in a clear, straightfor-
ward manner. In a very short
time I had coded and was play-
ing 28 measures of "Born Free"
in three voices.

The cassette tape has the
music operating system in
CUTS format on one side and
300 baud Kansas City format
on the other. After loading the
tape (4K starting at 0000H is re-
quired; 8K or more is recom-
mended) and executing 0000,
the command processor is
ready for your instructions,
most of which are self-explana-
tory (see Table 1).

FILE defines the amount of
memory used, and the starting
and ending addresses of the
current music file are dis-
played. SCORE takes the cod-
ing that you have entered and
compiles it as binary code for
the actual playing of the music
and displays where this code is
located. LIST displays the cur-
rent file for additions or correc-
tions; PLAY does just what it
says it does.

Coding a piece of music for

the "Music System" turns out
to be much easier than it first
appears. Table 2 is a list of
some of the symbols used.
Once the symbols for the
values of different notes have
been memorized, it is very sim-
ple to move across the page
coding one voice at a time. The
system can handle three voices
(notes) at once and 32 notes per
voice per measure. Fig. 1 is an
example of a few measures
that have been coded.

Lines 0010 and 0030 are re-
marks; line 0040 defines the key
and tempo. The tempo can be
changed by increasing or de-
creasing the figures after the
equal sign. The tempo can also
be controlled by the computer
sense switches (Inport FF) to
give you dynamic control of a
piece while it is playing. This is
just one more reason for me to
extend my sense switches to a
point outside of my SOL for bet-
ter accessibility.

The cassette contains six
coded classical pieces, so you
can hear what computer music
sounds like before you try your
hand at coding. Load the oper-
ating system, load one of the
six selections and PLAY for a
pleasant surprise.

I believe that I have found
one error in the manual. The
coding example shown gives
the key and tempo as:

0060 K2&
0070 NQ-50

My system prints error mes-
sages unless I place both key
and tempo on the same line as
shown in Fig. 1c (line 0040). The
selections recorded on the cas-
sette tape also use one line for
both.

The "Music System" was
written specifically for the SOL
and the I/O routines that it con-
tains on PROM. Six pages are
devoted to helping non-SOL
users write the patches neces-
sary to read the CUTS format
tape and to access their own
screen print routines.

Many other features are pro-
vided in the system, and though
I don't understand all of the
music terminology used, I am
sure it won't be long before I am
using every available function.

Here is a quick, simple and
inexpensive way to get into

computer music and impress
your friends and family as well.
The results are outstanding,
educational and, above all, just
plain fun! For music with a dif-
ference PLAY a little uncoded
memory— your monitor PROM,

for example. Now there is
music out of this world! ■

Software Technology Corp.

PO Box 5260

San Mateo CA 94402

(415)349-8080

V-

(

O-

T&~*

M3
O

Fig. 1a.

Qi 1

OtT^f

OS 6

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O, W *

♦ PLUS

MINUS

oT^-e

n °-«

o ^ r

Q9^e

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Fig. 1b.

0010 / NO SONG

0020 / BY ROD HALLEN 12-21-77

0030 /

00U0 Kl# NQ-50

0050 PA

0060 Ml V1*Q6Q7I819Q.8 V2@H1H2 V30H3HU

0070 M2 V1*H7H6 V2@H3H2 V3@H5W*

0080 M3 «W7 V2@W1 V3@W3

0090 MU ♦H8H$ V2@H2H$ V3(3Ht»H$

0100 PB RA

0110 PC

Fig. 1c.

Fig. 1. The music and the coding. Lines beginning with I are
remarks and are stored and displayed but not compiled. Line 0040
indicates the key of F# and says make a Quarter note equal to 50
iterations of a loop in the tone generator. More or less determines
the tempo. 0050 defines the beginning of part A. 0060 is measure 1.
It reads— Voice 1 (V1)— Treble Clef (*)— Quarter note 6 (Q6)—
Quarter note 7 (Q7)— Eighth note 8(18)— Eighth note 9 (19)— dotted
Quarter note 8 (Q.8). V2, V3 and 0070 to 0090 read the same way.
0100 indicates that part B will be a repeat of part A. 01 10 will be the
beginning of part C. Once coding is learned, many of the symbols
that are shown can be left out since note value once set will remain
the same until reset. As an example: Q6Q7I8I9Q.8 could be written
Q67I89Q.8.

Build a
Serial-to-Parallel Converter

Connecting parallel devices to serial ports is a snap. If you doubt it, read this article.

Serial-to-parallel converter in enclosure. Unit will accept either serial
TTL or RS-232 inputs while also providing similar outputs to be used
elsewhere. Parallel TTL outputs are available through a ribbon cable at
the rear of the enclosure, shown here with a DB-25 connector.

F. R. Ruckdeschel
773 John Glen Blvd.
Webster NY 14580

After two years of sol-
dering, I am embar-
rassed to confess that my
software files can all be
stored on three C-60 cassettes
(300 baud). Although suffi-
cient hardware has been in
place for more than a year to
do general programming, the
satisfaction of making shiny
solder connections has be-
come an obsession; 22-slot
Imsai motherboards are par-
ticularly inviting with their
2200 connections. The

therapeutic value of relaxing
over a hot soldering pencil
must be similar to the satis-
faction derived from knitting.
However, a point is even-
tually reached at which the
guilt of not using the com-
puter (an Imsai) for its in-
tended purpose becomes
overwhelming.

I reached this point
recently and made a resolu-
tion to concentrate on soft-
ware. I sat down at my dual
CRT terminal and began to
dream about creating some
money-making software, or at
least a game. It was about
time the graphics display was
used for something other

than checking whether or not
it worked. As I started to
type in a little program, the
line overwriting of the ter-
minal became intolerable.
Thus, the terminal was dis-
assembled, and the line-feed
signal was jumpered to the
line erase on the cursor
board.

Now I was ready to go
again. After a few hours, it
became apparent that the
paper-saving CRT display was
helpful in forest conservation,
but was also confusing when
trying to remember where to
jump to in a program (or
where one jumped from).
Obviously, hard-copy output
was needed.

Coincidental ly, I had pre-
viously constructed a PR -40
printer (actually, only the
interface). However, the
printer interface required
seven-bit parallel input plus a
strobe. All I had immediately
available was the parallel port

used with the graphics dis-
play. My first thought was to
design and build or buy — in
kit form, of course — another
parallel I/O for the Imsai.
However, remembering my
resolution, I decided to build
a small serial-to-parallel con-
verter that would simply tap
into the RS-232 line coming
from (or going to) the ter-
minal. Obviously, an etched
PC board was required to
assure the esthetics of sol-
dering. This was the origin of
the schematics and foil pat-
tern shown in this article.

Operating Features

Before I could charge
ahead, a few of the operating
features needed to be estab-
lished:

1. The parts used had to be
on hand. 1 used a 7400 quad
NAND gate as an inverter.
The clock required for the
universal asynchronous re-

lOufd

-> +12 TO +15 INPUT

220

5 VOLT
ZENER

■0+ 5 OUTPUT

-> gnd

Fig. 1. Five volt power supply.

ceiver -transmitter (UART)
was to be based on a 555
timer. I did not have the
UART itself, but chose the
AY-5-1013 for its price
(about $6) and particular
abiUty to be used for five-bit
reception. Someday, copying
Baudot might be desired.

2. The interface was not to
create any software over-
head. After all, in spite of the
resolution, I had always
avoided software; so why
change? Thus, the interface
was required to create a data
strobe to go with the parallel
output.

3. The unit had to be flexible
in baud rate and data format,
mandating the use of trim-
pots and switches.

4. The parallel output line
was to have LEDs to display
the actual data format. This is
useful in deciphering a ter-
minal's parity and data bit
number. This feature has
been useful in determing Mits
computer terminal formats
since, for some reason, that
information is missing from
my manuals.

5. Flexibility was to be main-
tained to cope with unfore-
seen situations, such as neg-
ative logic signals.

The schematics shown in
Figs. 1 through 4 accomplish
most of the above goals at a
low cost. The circuitry is
fairly simple and has worked
reliably for several months.

Circuit Description

Power supplies: The AY-
5-1013 UART requires sup-
ply voltages ot +5 and -12
volts, nominally ±5 percent.
As I have previously needed a
buffered RS-232C signal, one
additional supply require-
ment of +12 volts was added.
Those voltages can all be de-

rived from a ±1 5 volt op amp
supply; 250 mA capacity is
more than sufficient.

As the load current re-
quirements are fairly low,
simple zener regulation was
used. The filter capacitor is
on the source voltage line to
keep ripple away from the
regulation voltage level.

The 5 volt supply shows
two parallel 220 Ohm cur-
rent-limiting resistors. One is
sufficient if the optional data
output LEDs are not used. If
the source voltage is not 15
volts, some experimentation
will be required to determine
the proper current-limiting
resistor.

Resistor values shown
were chosen by putting the
entire unit in operation (all
LEDs on) and adjusting the
net resistor value (starting
high) until 30 mA of the load
current was passing through
the zener. This appears to
give a sufficient regulation
margin and does not lead to
excessive power dissipation in
the 5 volt zener.

Clock: The circuit shown
in Fig. 3 provides a TTL
square wave output whose
frequency is dependent on
the values of R and C. A
choice of two frequencies is
available through switched
trimpots R-j and R2. For my
purposes, the two frequencies
of interest were 300 and 600
baud, and the corresponding
component values are C=.003
uF with 10k Ohm and 500
Ohm trimpots. The clock is
best set using a digital
counter and setting the fre-
quency to 16 times the de-
sired baud rate. A second
choice is an oscilloscope
comparison with the 60 Hz
line frequency. A third choice
is trial and error, which is not

lOufd

-ognd

12 VOLT
ZENER

->- 12 OUTPUT

220

Enclosure disassembled. Front-panel connections are shown at the left
Main board contains a DIP socket for the parallel output ribbon cable.
Immediately below the DIP socket is the UART. Immediately above are
the eight optional LED indicators that show the status of the parallel
output lines. In the upper middle area of the circuit board is a DIP
switch for choosing parity, number of stop bits, etc. Directly to the
right of this switch is the 555 clock generator, above which are the two
trimpots for frequency (baud rate) control. The power supply is out of
view beneath this board.

-OTTL CLOCK OUT
(I6X BAUD RATE)

Fig. 3. Clock source for determining the bit rate (baud).

•> -12 TO -15 INPUT

Fig. 2. Negative twelve volt power supply.

difficult if the data LED
indicators are used. Although
I was apprehensive about
clock stability, this has never
been a problem.

Serial- to-parallel con verter
section: The AY-5-1013 is
fairly easy to use. The TTL
serial input is obtained from
the emitter follower transis-
tor arrangement shown in
Fig. 4. This transistor is
biased so that with no input
(open input line), the emitter
resides at approximately
volts. If a transistor other
than a 2N2923 is used, some
adjustment of the bias resis-
tors may be required. The
emitter generally follows the
input signal, though the
negative swing is more limited
than that in the positive
direction. This asymmetry
causes no trouble at all with
the eventual TTL level and

causes little difficulty with
the buffered output.

The buffered RS-232C
signal is converted to TTL
levels by a 5 volt zener diode.
The small (* .6 volt) negative
swing of the signal at the
zener side of J5 is acceptable
to the circuitry that follows.

The J5 jumper position is
a key signal node. With a
RS-232C signal input, the
TTL signal may be fed
directly to the UART input
or may be inverted. Normal
RS-232C signals use negative
voltage swings to represent 1
and positive swings to repre-
sent 0. Thus, inversion is
required. This is accom-
plished through the jumper
between J5 (right) and J6,
which inserts an inverter in
the signal path. The zener
side of J5 also offers an entry
point for TTL serial input

signals. Again, the inversion
option is available.

What the UART does with
the input is determined by
the 5 control bits (EPS, NB1,
NB2, TSB and NP). These
bits are selected by the 5 DIP
switches at the lower right of

the schematic; a pull-down
arrangement is used, the con-
trol bits are always enabled as
the control strobe (CS) input
is hard-wired to a logic 1
level.

Other control signals
permanently enabled are SWE

and RDE . These cause the
status word bits and received
data bits to be continually
and immediately placed on
their respective output lines.
In the case of the parallel
output lines, LEDs containing
internal resistors are used to

Item

Quantity

Integrated circuits

LEDs

Zeners

Transistors

Capacitors

Resistors

Switch

Power supply

PC board

Description

AY-5-1013 UART (General Instrument part;

obtained through James Electronics).

555 timer.

7400 quad NAND gate.

Internal resistor LEDs (Polypaks: order extras

as the yield rate I observed was 6/8).

LED (almost any low-current device will do).

12 volt.

5 volt.

NPN with reasonable breakdown characteristics;

2N2923.

1 uF tantalum, 25 volt.

.003 disk (depending on baud rate).

.01 disk.

.1 disk.

220 Ohm, 1 Watt.

330 Ohm, 1 / 2 Watt.

1 k Ohm, 1 / 2 Watt.

3k Ohm, 1 / 2 Watt.

4.7k Ohm, 1 / 2 Watt.

10k Ohm, 1 / 2 Watt.

33k Ohm, 1 / 2 Watt.

Trimpots (depending on baud rate).

16-pin DIP switch.

±1 5 volts @ 250 m A worked well.

Single-sided, etched but undrilled board is available from the

author for $7.50. New York State residents, add sales tax.

Table 1. Parts list.

indicate the output logic
levels.

A strobe (active low)
signal is automatically created
upon reception of a serial
input character. Such a strobe
is required by the PR-40
interface. It can also be con-
veniently used to enable Tri-
state buffers leading to a data
bus, etc. This strobe is gener-
ated by the two inverters
appearing at the lower left of
Fig. 4. The data available
(DAV) signal from the UART
is used as the initiator for this
signal. The DAV flip-flop
signal is inverted by the 7400,
the output of which is the
active low signal desired.

However, unless the DAV
flip-flop is reset, this signal
does not return high to do
the same for the next char-
acter received. Thus, the sig-
nal is again inverted and, after
an RC delay, applied to the
external reset (XR) control
on the UART. This resets all
the UART flags, including
DAV. The reason for using
XR and not DAV reset
(DAVR) is to ensure that at
some later date the error flags
(OR, FE and PE) may be

RS -232 INPUT <-

BUFFERED RS-232 OUTPUT <-

♦ I2T0-H5

TTL
INPUT/OUTPUT

* 2

33K

I0K

r>*oo /

DATA/POWER LED

*00

/
/

/ INVERT

JUMPER

J5 L. J

NON-INVERT

JUMPER

"5" 5 VOLT
ZENER

/ w

TTL INPUT S

DAV FLIP-FLOP

lil

J I L

Ico

cr
o

LlI U_ _
Li- Q- O

(8) INDICATOR LED'S
W/ INTERNAL
RESISTORS

JJJJ

CVJ

<0
o

PARALLEL OUTPUT

AY-5-1013 UART

1^7400

cr
x

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DATA STROBE
OUTPUT

r
i

oooooooo

K <r

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o
o

I I I I I I I

PARALLEL
INPUT

Q_ CO CD CD < Ar >
I- -Z 2 (t 40

Fig. 4. Conversion section of serial-to-parallel converter.

conveniently monitored. With
the components shown in
Fig. 4, the strobe pulse length
is seven microseconds. (For
those who have attempted to
interface their PR -40s direct-
ly to a Mits parallel I/O,
there is a small problem: The
output strobe duration is too
short. A pulse stretcher
[greater than one micro-
second] is required.) The

parallel output signals, along
with the strobe, are all that
are required to drive the
PR -40.

Other circuitry: To indi-
cate both the presence of
power, signal and signal
polarity error, the simple
data/power LED circuit was
added. If the converter is
turned on but not connected
to a serial input line, J6 goes

to a logic 1 state and the LED
is enabled. If the signal line is
connected but there is no
data transmission, a mark
signal is received. If this mark
leads to a TTL 1 level, the
LED stays on. If the signal
line polarity is wrong, the
LED goes out, indicating a
fault; changing the jumper
corrects this. If the power is
on and the signal line polarity

correct, then a data signal is
apparent by flicker in the
LED.

Also included on the
printed circuit foil pattern are
provisions for parallel-to-
serial conversion using the
existing clock. The required
parallel input and strobe
signals may be obtained
directly from a typical Mits
parallel I/O board. Note,

Fig. 5. Printed circuit foil pattern.

however, the serial output
signal is TTL level and not
RS-232C. A simple transistor
circuit could easily be de-
signed to translate the logic
levels.

It should also be noted
that the flags associated with
parallel-to-serial conversion
can be reset by a serial char-
acter input, as XR is activated
upon reception.

Converter Operation

The operation of the
serial-to-parallel converter is
straightforward. Simply
connect the input and output
lines. However, there is one
operating characteristic of the
PR-40 mechanics that must

be accounted for: slow print
head return. If the converter
is hooked to the terminal
transmit line, there is no
problem; a one-second wait
after a carriage return is
sufficient. If instead the con-
verter is connected to the
terminal receive line, it is
possible that data may be
received during a print cycle.
This may mess up the printed
line or data may be lost. Such
a situation may be avoided by
use of a software delay (at
last, software). Most of the
larger BASICS have a null
command, which can be used
for such a delay.

Although the setup is fair-
ly foolproof, I have managed

to accidentally create a
curious fault. It is possible to
set the serial transmission
format (parity, stop bits and
number of data bits) vari-
ously different on the com-
puter Sl/O board, terminal
and converter so the terminal
receives and transmits with-
out display error; but the
converter, when placed on
the terminal receive line, gives
the printer "correct" data
only upon terminal echo, and
not with computer-generated
text. Thus, a little consis-
tency in format is necessary.

Epilog

Once the printer was on
line through the serial/parallel

A kit for building this project is available from: O.C Stafford Electronic Service
and Development Co., 427 S. Benbow Rd., Greensboro NC 27401.

PC board: $7.50, drilled; $5.80, undrilled (part no. KB 2-78)

Negative or positive: $3

Parts kit (no board, no PROM), $27

PROMs: 1024 x 8, $39.50; 512 x 8, $15

Add $1 for shipping

converter, the beauty of CRT
displays became evident. It is
easy to create yards of print-
out, again making it difficult
to determine what was done
and, more important, keep a
concise log. My response was
to connect the converter to
the terminal's transmit line.
In this way, all the statements
typed are recorded, and not
the returning prompts, syntax
errors, etc. Also, the printer is
in a local mode and can be
used to record what was pre-
viously handwritten in my
notebook — whether or not
the computer is on (or
working).

Now to concentrate on
software. ■

1st Prize: Mullen Controller Board Kit

with 2 AC power modules

2nd Prize: Mullen Extender Board Kit

Since we redesigned the Relay/Opto-isolator Control Board
and brought its price down to $88, we've heard about lots of
applications. Robots. Solar energy. Model railroads. Disco
lights. Time lapse photography. Even an automatic cat feeder.

But we want more applications to include in our continuing
series of applications notes, and this is where you come in.

In case you haven't seen our Controller Board, it includes 8
reed relays that respond to an 8 bit word; additionally, 8 opto-
isolators accept signals from the outside world for hand-
shaking or further control purposes. In essence, you have a
switching system with all the intelligence of a computer at
your command.

So, let your imagination run wild, then tell us your idea for
an application . . . you just might win a free way to implement
that idea.

Contest Rules: For further information on Mullen Computer Products, visit your local
computer store or write us. All entries must be postmarked no later than midnight, Dec.
15, 1978, and become property of Mullen Computer Products. Enter as often as you wish.
Duplicate prizes awarded in case of tie. Please print your name clearly on the entry. Try to
keep descriptions short, but if you get carried away describing some fantastic scheme
we'll understand. Good luck, and we look forward to hearing from you.

MULLEN Com pot

BOX 62 1 4, HAYWARD, CA

Totally Integrated, Entirely Self -Contained

PERSONAL COMPUTER

With technology so advanced,

Concept so remarkable,

Operation so utterly simple,

Cost so incredibly low.

The PET has given rise to a brand new era...

The Age of the Personal Computer

HIGH SPEED PRINTER
ACCESSORY

Immediate Delivery

FEATURING AN IEEE 488 BUS

The PET, unquestionably, has become the standard
for the personal computer industry. As such, con-
sumer and business publications have lauded its
discovery. It comes out of the box, plugs into the wall,
and is ready to use.

IN A LEAGUE WITH IBM, HP
AND WANQ MINICOMPUTERS

The fully integrated PET is a minicomputer and should
not be confused with game products that hook up to
household TV's. What sets It apart from other
computers It price. While others cost from $11,000 to
$20,000 and more, THE PET, with similar power, Is only
$795.00.

It is of sufficient size and speed to accomplish many
of the routine computational tasks facing engineers
and scientists. By combining an extended BASIC
interpreter with one of the fastest microprocessors
available, Commodore has created an incredibly
capable, yet inexpensive, computer.

POWERFUL 6502 HARDWARE:

The mind-boggling PET has all necessary functional
elements packaged in a single cabinet. Its CPU is a
MOS Technology 6502 8 bit microprocessor which can
address 65,536 bytes of memory directly. It has 56
instructions and 13 different addressing modes.
Depending upon address mode, instructions are ex-
ecuted in 2 to 7 microseconds. The unit has 9216 bytes
of random access memory (RAM) and 16,384 bytes of
read only memory (ROM). 1K of the RAM and 2K ROM
are used for video display. 1000 characters, organized
in 25 rows of 40 columns can be displayed at a time.
An 8x8 dot matrix delivers superb CPU readability.
The character set consists of 158 upper and lower
case letters, numerals, punctuation symbols and a
variety of graphics characters.

Bar Graphs

Amortization Chart

Black Jack

Teaching Trigonometry

All characters can be displayed in normal mode -white
on black, or reverse • black on white. Since the display
is part of main memory, it can be accessed directly by
the CPU. Flexibility is enhanced by the full screen
editor. Input is either from the 10-key numeric
keyboard, with its full cursor control, or the built-in
cassette tape drive. All symbols used in BASIC
statements are available in the unshifted mode for
added operating speed. The cassette can be used to
read and write programs and data at 50 bytes per
second. A second cassette port, 8 bit parallel I/O port
and IEEE-488 bus port are also provided. The entire
system weighs 38 lbs. and measures approximately
15V2"hlghx 17Y4"widex I8V2" deep.
The PET is completely silent in its operation. No
special installation is necessary because it operates
on ordinary 1 10V household current at 50-60 Hz.

INCREDIBLE FIRMWARE FLEXIBILITY

The firmware's three primary components include the
operating system, full screen editor, and BASIC inter-
preter. Together these programs use 14 K bytes of
read only memory.

DIRECT ACCESSORY PLUG IN

The unit's operating system permits you to easily load
and save programs, one of its exclusive features is
complete support for the IEEE-488 instrument bus,
which is occasionally referred to as an HP-IB bus. This
bus provides superb flexibility. Through it, you can
connect up to 12 devices to the PET, at the same time.
This universal port permits direct connection of the
PET Printer, in addition to a wide variety of measure-
ment and control instruments such as counters,
timers, spectrum analyzers, digital voltmeters and
printer plotters, from HP, Phillips, Fluke and
Textronix. Many academic, industrial and govern-
mental labs are already using PETS as laboratory
automation control computers.

With the PET's full screen editor, an entire program, a
selected section, or a statement can be listed. The
cursor can be moved as needed on the screen, and
characters can be changed, inserted or deleted to
modify any program statement. Statements can be
copied or moved by changing their line number. New
statement scan be added, or old deleted, as desired.

COMPLETE COMPUTER PERFORMANCE

The BASIC interpreter enables a superset of the
original BASIC. Among its major features are floating
point, integer and string arrays of limited dimen-
sionality, dynamic string handling, 5 byte floating
point number representation (for approximately 8
decimal digit accuracy), PEEK and POKE commands
for direct memory access, two character variable
names, full support for IEEE-488 bus devices, program
chaining with full data retention between overlays,
built-in mathematical (ABS, ATN, COS, EXP, INT, LOG,
RND, SGN, SIN, SQR, TAN) and string (ASC, CHR,
LEFT, LEN, MID, RIGHT, STR, VAL) functions; user-
definable functions; multi-statement lines; real-time
clock; support for machine language subroutines;
both character and line input capability.

HIGH SPEED PET PRINTER

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Application programs for the PET can of course be
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D Basic Math Package:

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Chi-square test for independence between two

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Expansion Time!

S-100 Memory for SWTP System

With ingenuity, you can use S-100 memory boards in your SWTP machine . . . a dollar-saver.

Stuart Mitchell
14761 Dodson Dr.
Wood bridge VA 22193

Phil Poole

1408 Idaho

Wood bridge V A 22191

Completed assembly with 28K of memory installed. Note fan mounted on cover for cooling memory.
90

Money and memory are two
things you can never have
enough of for your microcom-
puter. Although the SWTP 6800
computer with 4K memory
sounds like a great deal (other
processors come with even
less or no memory at all), you
will soon discover that 4K isn't
enough to be useful. Prompted
by several friends, we came up
with additional memory for the
6800. You'll find this solution is
similar to our Mits 680b mem-
ory expansion ("Make Your
680b Smarter," Kilobaud No. 3,
p. 102), except that it's less ex-
pensive . . . nothing needs to be
done about the power-supply
requirements. We hope this ar-
ticle will alleviate your money
and memory shortage, at least
temporarily.

Theory

There is nothing magical
about saving money— the more
of something you produce, the
lower the cost and selling price.
The so-called S-100 memory is
a good example. Ithaca (NY)
Audio's bare memory board
(which sells for $25) and a little
judicious parts ordering will net
you 8K of 450 ns static memory
for about $120. Although it
sounds easy— order the parts,
assemble according to the in-
structions and plug it into your
SWTP 6800, and presto, 12K of
memory just like that— there is
a catch. It won't plug in be-
cause the sockets don't match.
Correcting this situation is
what the rest of this article is
about.

The 6800 will take 32K of
memory (remember, 4K came
with your computer). Many
S-100 static memory boards,
like S.D. Sales 4K and Ithaca
Audio 8K, are available. We
have laid out a PC extender that
will take up to five boards. To
experiment, we used four S.D.
Sales 4K boards, temporarily
borrowed from other comput-
ers, and a new 8K board from
Ithaca Audio. All went well.

The only interconnections
that aren't straightforward are
the connections of the S-100
Data In and Data Out buses to
the bidirectional bus in the
6800. If memory boards like the
8K Ithaca Audio or the 4K S.D.
Sales are used, simply tie the
corresponding data lines to-
gether; the R/W line will select
the appropriate Tri-state buffer.
A,s. «j.£u.aJ., the R/W U<\e must be
inverted, and the protect fea-
tures not enabled.

Construction

Collect the parts and pieces
for the memory boards. We sug-
gest you buy the maximum
number of ICs on your first pur-
chase since the 21L02s are
cheaper by the hundreds (call
Ithaca Audio for current
prices). Share the expense with
several other people to save a
few extra dollars on the
memories.

Etch the extender card using
single-sided copper-clad board
using the photo layout in Fig. 1.

If you use the Calectro Kit for
making printed circuit boards
directly from this magazine,
check to insure that there are
no holes in the solid black
areas; if there are, use india ink
to fill them in before process-
ing. Sockets for the S-100 are
standard .125-inch pin spacing
and .250-inch row spacing.

As usual, we have chosen to
use the spliced-socket method,
which reduces the cost since
odd-length sockets are avail-
able at most surplus houses.
Add two socket pins together
to give you more than 100 (50
each side); this is required. We
found that using a hacksaw is
the easiest way to cut them; but
leave two extra pins on each
socket. Grind or file each sock-
et down to the final dimension.

Using this method reduces
the total cost for the S-100
sockets from $20 to about $5.

The SWTP sockets for the edge
of the extender card can be ob-
tained from SWTP ($3/set), or
see your local General Electric
TV repairman and get them off
the bad TV plug-in modules
(boy, are we cheap!).

Mount all sockets on the
printed circuit card and solder
them in place. It is OK if you
don't mount all the S-100
sockets, but use the bottom
slot because the pins make a
good point to connect the jump-
ers to the SWTP bus. Use the in-
terconnect chart to determine
which pins go together.

There is one 5 volt regulator
(7805) and a filter capacitor to
be mounted on the 6800 extend-
er card. It is used for IC1, which
is a 7404. This inverter is used
to invert the signal from pin 47
and send it to pin 68 of the
S-100 bus. S-100 pins 45/46
must be grounded for the

Ithaca Audio 8K board to be ad-
dressed properly. Well, that's it
for the 6800 extender board.

We strongly recommend that
if you use very many memory
cards, you install a muffin or
whisper fan for cooling the new
memory cards. As you can see
in the photos, the fan mounts
on the cover with four small
bolts; no modification is need-
ed to the SWTP cover. Wire the
fan in parallel with the primary
of the power transformer.
These fans are available from
several mail-order houses for
about $5-$7. Be sure to unplug
your computer when wiring in
the fan\

To test the extender card,
plug it in the third slot from the
front of the computer with no
memory cards installed. Now
install the CPU card in slot one
(closest to the front panel); the
original 4K memory is installed

6800

6800 Buffer In Buffer Out S-100

S-100

Designation

Pin # Pin # Pin # Pin #

Designation

DI0

DO0

D01

DI2

D02

DI3

D03

DI4

D04

DI5

D05

DI6

D06

DI7

D07

A15

A14

A13

A12

A11

A10

R/W

SMEMR

R/W

41 IC1,1 IC

1,2 68

MWRITE

Table 1.

in slot 2, and the I/O cards re-
main unchanged in the back.
Turn the computer on and
check supply voltages. The
7404 (IC1) should have five volts
between pin 14 and 7. Check
S-100 pins 47 and 68; they
should be inverted from each
other.

If all is OK, power down the
computer, insert one memory
card, power up, and you should
be ready to run your favorite
memory-check program. Don't
forget where you addressed the
additional memory card. If the
memory check didn't work,
check the switches or jumpers
on the newly installed memory
to make sure they are properly
addressed.

Conclusions

The extender card is easily
built, inexpensive and
operable. Several are in use
already. As one fellow said,
"It's so simple I should have
done it last year." Up to 32K of
memory is possible, so five
slots are enough if 8K memory
boards are used. The main
disadvantage is that the S-100
memory cards use up the SWTP
bus slots. There may be other
physical configurations; we
would like to hear your ideas.

For other experimenters, a
full-size positive or negative PC
layout is available for $7.50. An
etched, plated and undrilled
printed circuit card is available
for $15 from the authors. ■

White spacers visible on right edge maintain vertical spacing of
the memory cards.

ATTENTION

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Fully Assembled and Tested $198 2 $375
Complete Kit $175 2 $330
Blank PC Board $39

D&N MICRO PRODUCTS d 3 4

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TERMS : Check or money order. Add $4 shipping and
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ANNOUNCING THE
BYTE BOARD

A Better EPROM Board

Better because . . .

• It holds 16 2708s • Each 2708 is individually ad-
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do not take up memory space • Power On Jump
available for front panel-less operation • S-100
bus compatible • Comes with a 20+ page
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complete with sockets and all parts except
EPROMs.

Compare. You can pay more, but you can't buy a
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Want EPROMs? We've got 2708s for $10 ea,
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213 842 2866

D32

ATTENTION
APPLE II OWNERS

Southeastern Software announces
ready to run programs on tape for
your computer . . .

Send $5.95 plus 50* postage and
handling for demo tape and sample
newsletter designed for Apple II
owners.

Demo tape includes 1 game and 2
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m 7270 Culpepper Drive S52
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16526 Buchet Dr.
Granada Hills CA 91344

What Is a Bus?

A computer's bus is a lot more than something to plug boards into . . . especially if you're
designing or troubleshooting it.

Every modern computer
uses buses for the inter-
connection of its parts. This cir-
cuit structure is familiar to
computer hobbyists, but for
persons with experience in
other fields of electronics, the
function and peculiarities of
buses can be confusing; for the
novice in the field of elec-
tronics, buses can be outright
puzzling. In this article I will at-
tempt to give a systematic
description of the various types
of buses that can be en-
countered in a computer.

A Bus is a Bus

by Any Other Name . . .

Bus is an abbreviation of
omnibus. Few people who
board a bus for a trip to the air-
port or across town would give
a second thought to the roots
of this word. Like many words
of daily use, it has its origin in
Latin. Omnibus (my old Latin
teacher would be proud of me)
is the dative plural form of the
word omnis meaning all.
Omnibus, therefore, means for
all or, loosely translated, for
everybody.

At a time when people trav-
eled in private horse-drawn
coaches, a vehicle for the con-
venience of everybody was
called an omnibus and the
name has stuck not only for
vehicles, but also, generally, for
any commodity for the benefit
of more than one person. That
explains the omnibus bills that
appear— usually just before
summer recess— in state and
federal legislation and have
nothing to do with transporta-
tion, but are just vehicles to
give senators or congressmen

a chance to propose a law of
their own.

Power Buses

In electricity, buses have
been around long before there
was such a thing as elec-
tronics. Normally, an electrical
connection or a wire goes from
one point or terminal to another
point or terminal. But frequent-
ly, connections interconnect
more than two, and sometimes
many, points in a circuit. Such a
connection may be called a
bus, and bus-bars can be found
in every electrical distribution
panel where they connect the
incoming power line to the vari-
ous circuit breakers.

In a computer (or any other
electronics device), a power-
distribution bus connects the
power supply with the many cir-
cuit boards and distributes the
power to the individual circuit
components. Because these
power buses often have to
carry relatively large currents,
they frequently are hefty wires
or, in printed-circuit boards,
they are implemented with
traces that are wider than the
other circuit traces, which carry
only information.

Message or Information Buses

In the majority of the buses
within a computer system, in-
formation, rather than power, is
ported over the bus. In this
case, one or more devices send
out electrical pulses that repre-
sent messages that are re-
ceived by one or more other de-
vices. In one particular stan-
dard for bus systems (IEEE
488), these devices are called

either talkers or listeners, ac-
cording to their function. These
names convey an excellent
idea of what is happening in the
process of information transfer
and shall be used in the fol-
lowing.

One Talks and Many Listen

The simplest data bus is one
that connects one talker to
several listeners. The flow of in-
formation is obviously unidirec-
tional (namely, from the talker
to the listener), and the bus is
nothing more than a simple
connection from the output of
the talker to the inputs of the
listeners. Because every listen-
er input presents an electrical
load to the bus, the output of
the talker frequently has to be a
bus driver, a circuit that can
provide all the power required
by the load in a short time.

Such buses can consist of a
line or lines that together are
considered a bus. Examples of
the single-line buses are the
clock-pulse line and the Read/
Write line (both of which are
usually not called buses in the
manuals). In both of these
buses, the microprocessor
does the talking and every
other device in the system just
listens.

The best example of a bus
consisting of several lines is
the address bus, which usually
is 16 lines wide. On this bus,
too, the microprocessor does
all the talking while the other
devices listen. (An exception to
this situation is the so-called
DMA, or direct memory access,
where, on occasion, some
other device talks on the ad-
dress bus. Obviously, you have

to make sure that the micropro-
cessor does not talk at the
same time because utter confu-
sion could result. This can be
avoided by temporarily discon-
necting the microprocessor
from the bus.) These unidirec-
tional buses are the simplest
type, but things can still go
wrong.

One problem that can occur
is bus loading. The devices con-
nected to a bus are designed by
their manufacturer to safely
read a voltage level as a logical
or 1 if it is below or above a
certain level. For TTL-type de-
vices these levels are usually
about .8 volts and 2 volts.

If too many loads or devices
are connected to a bus, the bus
driver may be unable to drive
the bus voltage to these values
(or may take too long to reach
this value). Instead of a high
voltage of 2 volts, it might just
barely make it to 1.9 volts, for
example. Most devices con-
nected to the bus are likely to
still interpret this voltage as a
1, but their manufacturer does
not guarantee that they will. In
this case, all kinds of bad
things can happen. So, the load
on a bus and the bus driver
have to be matched in order to
make sure that doesn't happen.

Other problems are crosstalk
and bus reflections. Both ef-
fects result from every bus
line's having a capacity with re-
spect to other bus lines and to
ground. The capacity-to-adja-
cent bus lines can cause cross-
talk (i.e., a pulse on one bus line
is capacitively coupled to some
other bus line).

The capacity-to-ground —

together with the inductance
that every wire represents —
can make a bus act as a kind of
resonant tank circuit. The
result is bus ringing, which can
cause false voltage readings,
especially when fast or short
pulses are used.

The shielding of bus lines
(usually by a groundplane) and
the termination of buses by re-
sistors (or clamping diodes) can
help reduce this problem. The
S-100 bus — because of its
many closely spaced bus lines
— seems to have been troubled
by both problems on occasion;
several companies offer S-100
backplanes that utilize ground-
plane shielding and bus termi-
nations to overcome the prob-
lems.

One Ear for Many Talkers

The opposite of the bus just
described is one that connects
many talkers to one listener.
Obviously, if more than one
talker talks at the same time,
the listener might not be able to
understand what is being said,
although he knows that some-
body is trying to get his atten-
tion.

An example of this type of
bus is an interrupt line, which
allows any one of several de-
vices to signal the micropro-
cessor that it requires service.
The solution to this problem ap-
parently is to simply connect
the output of several devices to
the appropriate input of the
microprocessor. If you try to do
that, however, you have to
observe some of the peculiar-
ities of the devices used for this
game.

The output of the normal
TTL-integrated circuits has a
so-called totem-pole configura-
tion. (With CMOS circuits the
situation is similar.) This
means there are two transis-
tors at the output, with one sit-
ting on the shoulders of the
other one. The effect of this ar-
rangement is shown in Fig. 1.
The output of the device ap-
pears to be connected through
a closed contact (which, of
course, is actually a transistor)
either to +5 volts or to ground,
depending on whether the
device tries to puff the output
line to a logical high or low.

INPUT

OUTPUT

Fig. 1a. Circuit diagram of a
TTL gate or inverter with totem-
pole output. (Transistor A sits
on the shoulders of transistor B
like figures on a totem pole,
thus, the name.)

♦5V

I
I

NORMALLY
CLOSED

INPUT

.I >

OUTPUT

v* NORMALLY
'\ OPEN

Fig. 1b. Equivalent circuit in
which the two output transis-
tors have been replaced with
the contacts of a relay.

That works fine until you con-
nect the outputs of two (or
more) of these devices together.

Now, if one of the devices
tries to pull the output line to
+ 5 volts while the other one
tries to pull it to ground, the two
closed contacts appear to pro-
vide a short circuit between + 5
V and ground. In reality, it is not
quite that bad, and you are not
likely to blow a fuse (maybe not
even an IC) when that should
happen; but the bus goes
neither to +5 V nor to ground,
but to some unpredictable level
in between.

Circuits with this output con-
figuration, therefore, cannot be
connected together; you have
to use another group of TTL de-
vices that have a so-called
open-collector output. In these
devices, transistor A, which is
the upper man on the totem
pole, has been left off and the
output is simply the collector of

transistor B. In order for this de-
vice to function properly, an ex-
ternal collector resistor has to
be provided.

As shown in Fig. 2, the col-
lector resistor can be connect-
ed to the output of more than
one device. Any one of the
devices then can pull the bus
line to a low level without inter-
fering with one of the other de-
vices. Or, to express it the other
way, the bus line can be in a
logical true (high) state only if
none of the connected devices
are in the logical or low state.
This connection scheme is
sometimes called the resistor
ORing of outputs, although
resistor NORing would be more
correct.

The Conversational Bus

In the buses discussed thus
far, the flow of information is
always in one direction— from
the talker or talkers to the
listener or listeners. It is some-
times advantageous to use a
conversational, or bidirection-
al, bus in which the devices
alternately act as talkers and
listeners, and the flow of the in-
formation changes direction.

The reason this type of bus is
frequently used as a data bus in
microprocessor systems is
very simple. Because the micro-
processor itself is nothing
more than an integrated circuit,
all its connections have to pass
through the pins of the circuit
package. The number of pins of
such a circuit package is lim-
ited, however. Using the same
pins for the input and output of
data saves eight pins (in an
eight-bit microprocessor) and
makes it worthwhile to use a
bidirectional data bus, even
though this arrangement is
slightly more complex than two
unidirectional buses.

In a bidirectional bus, two
special features have to be pro-
vided to ensure that the bidirec-
tional conversation functions
without problems. First, there
has to be some way to indicate
to all devices on the bus in
which direction the information
flow shall take place. For data
buses the Read/Wr ite (or more
accurately, Read/Write) line
takes care of this part.

If the microprocessor sets
this line into the high state, it
indicates that a read operation
is taking place. That means the
processor assumes the role of
the listener and expects the ad-
dressed device to talk. If the
microprocessor pulls this line
to the low level, it indicates that
a write operation takes place;
the processor talks and ex-
pects the addressed device to
listen.

Second, because every de-
vice can act as a talker or listen-
er, you have to ensure that no
device talks while it is sup-
posed to listen. Because both
the listen-input and the talk-
output of each device are con-
nected to the same bus, the
output has to be disconnected
from the bus in some way when
the device is in the listen mode.

To give a specific example:
The commonly used 2102 static
memory has separate pins for
Data In and Data Out. If you
write into the device via the
Data-in line, the same data ap-
pears at the Data-Out pin. If you
simply connect both pins to the
data bus line, all hell breaks
loose. The Data-Out pin, there-
fore, has to be disconnected
from the bus unless the Read/

Write line is in the high state, in-
dicating the processor is listen-
ing to the memory.

This disconnection of the
output of devices from the bidi-

♦ 5V

BUS INFORMATION FLOW

-€> -C -©

LISTENER

DEVICE

DEVICE 2

DEVICE 3

TALKERS

Fig. 2. The principle of the resistor-OR or wired-OR (more correctly
wired-NOR) circuit.

TO MICROPROCESSOR
AND OTHER
BOARDS

INFORMATION FLOW FOR WRITE
INFORMATION FLOW FOR READ

♦ 5V

•

LOAD
RESISTORS

TO BITS 2-7

CONTROL LINE
HIGH IF K SELECT
AND R/W"
AND 4>2 ARE HIGH

ADDRESS
DECODER

Fig. 3. A bidirectional bus system that uses open-collector gates to disconnect the Data-Out pins of
memory chips from the bus during a write operation. (Only two of eight bits are shown.)

rectional bus can be achieved
by the use of the resistor-NOR
principle described earlier. Fig.
3 shows such an arrangement.

The output of the memory
chip can control the state of the
data line, but only if the control
line is in a high state, which
means that the processor is ex-
ecuting a read operation and
wants the device to talk. If this
line goes low, the output of the
7403 open collector NAND-gate
is kept in a high state, no mat-
ter what the data output of the
memory chip does. (The invert-
er is necessary to provide a
double inversion so that the
signal on the bus is identical to
the one at the output of the
memory chip.)

The use of the resistor-NOR
technique for bidirectional
buses has one limitation, how-
ever. In larger systems the
capacitive loading of the bus,
due to the physical length of
the bus and the many devices
connected to it, can be quite
substantial. When the bus is
supposed to go into a high
state, this capacity has to be
charged by the current flowing
through the load resistor. This
resistor, therefore, should be
fairly small.

On the other hand, this
means that when the bus is in
the low state, a large current is
drawn by the device that is driv-
ing the bus low. There is, there-
fore, a limit on how small the
load resistor can be made and
how large a bus system can be
operated in the resistor-NOR
mode.

This limitation can be over-
come if the bidirectional bus is
designed with so-called Tri-
state devices. The principle of a
Tri-state output can be easily

understood by looking at Figs.
1a and 1b. In the totem-pole
output of a normal TTL device,
the two transistors A and B are
alternately in the conducting
and nonconducting state, thus
forcing the output high or low.
If, on the other hand, both tran-
sistors are in the nonconduct-
ing state, the output of the de-
vice is neither high nor low, but
is in a third state in which the
device is disconnected from
the bus.

In order to force the device to
go into this disconnect state, a
special input pin is provided
(labeled strobe, enable, select
or control in data sheets). The
polarity of this input can be
such that the device is discon-
nected if the enable input is in
the high state or if it is in the
low state.

With bidirectional bus sys-
tems being more common,
more and more TTL (and CMOS)
devices with Tri-state outputs
are becoming available. Table 1
shows the more frequently used
Tri-state buffers and inverters.

A special type of device is the
so-called bus transceiver. These
integrated circuits contain
eight inverting or noninverting
buffers with a common enable
input. When the enable input is
high, a group of four buffers is
enabled while the other four are
in the disconnect state. When
the enable input is low, the two
groups are reversed.

By properly interconnecting
the inputs and outputs of pairs
of buffers from both groups,
the bus transceivers can be
used as an interface between a
bidirectional bus and two uni-
directional buses, or vice versa.
They can also be used as
bidirectional buffers between

two bidirectional buses,
shown in Fig. 4.

There Are Buses and Buses

Most computer hobbyists,
when they hear the word bus,
immediately think of the S-100
(Altair) bus. Actually, the S-100
bus represents only one of sev-
eral bus types around, namely,
the systems or backplane bus.

The systems bus intercon-
nects the individual circuit
boards that make up the com-
puter. Physically, a systems
bus is only a number of circuit
traces on the backplane that in-
terconnect all equally num-
bered pins of the backplane
connectors. In electrical terms
—the systems bus is made up
from four different sub-buses.

1. The power bus distributes
the supply voltages to the cir-
cuit boards.

2. The address bus (usually
16 lines wide) is a unidirection-
al bus with the processor doing
all the talking while all other
boards are listening.

3. The data bus, in the S-100
bus, consists of two unidirec-
tional buses, one for read and

one for write operations, each
eight lines wide. On the proces-
sor board, bus transceivers are
used to interface these two
buses to one bidirectional data
bus that goes to the micropro-
cessor. Most other systems
buses (Heath, SWTP, OSI) use
bidirectional data buses
throughout the system. This
partially accounts for their
having fewer lines than the
S-100 bus.

4. The control bus is made up
from several different control
lines — all unidirectional. In
some lines the information flow
is from the processor board to
the rest of the system. In
others, the information flow is
reversed; every board can talk,
but only the processor listens.
The purpose of the control bus
is to inform the other boards
what the processor is doing. It
also permits the boards to talk
to the processor directly— for
instance, to tell it to WAIT be-
cause the board has not yet
finished an operation.

Note that the only lines of the
systems bus that extend be-
yond the backplane are usually
the ones of the power bus. Be-
cause the pulses on the signal
lines are usually fast and rise
times could be a problem, it is
actually not possible to extend
the systems bus by a couple
yards in order to connect to a
terminal.

The systems bus, however, is
not the only type of bus that you
can encounter. For example,
the IEEE 488 bus mentioned
earlier— also known as HP-IB
(Hewlett-Packard Interface
Bus, named after the company

Tri-state Buffers

Inverting

8T09(quad)
8T96,8T98(hex)
74366, 74LS366(hex)
74368, 74LS368(hex)
81 LS96(octal)
81 LS98(octal)

Noninverting

74125,74126(quad)
8T95, 8T97(hex)
81LS95(octal)
81 LS97(octal)

Tri-state Bus Transceiversfall quad)
Inverting Noninverting

8226

8T26A

8T34

8216
8T28

Table 1. Devices with Tri-state outputs.

that introduced it), IEC-BUS, or,
in Europe, EUROBUS— serves
a completely different purpose.
It is an interface bus that per-
mits the interconnection of up
to 15 different devices (com-
puters, printers, terminals, etc.)
by a single bus cable that can
be up to 20 meters (about 65
feet) long.

In many applications the 488
bus might eventually replace
the old RS-232C interface. This
interface permits the connec-
tion of one terminal to one I/O
port and, by definition, is not a
bus at all. The IEEE 488 stan-
dard, a book of 80 pages, is a
most comprehensive (and also
most unintelligible) document,
and the discussion of its de-

MICRO
PRO-
CESSOR

I
. READ BUFFER

I/4 8T28

BUS TRANSCEIVER

BIDIRECTIONAL

D7 1

8 DATA LINES

R/«-
♦ 2-

Nyrite b

I BUS

FER Ir/W

| *2

1/4 8T28

BUS TRANSCEIVER

TO OTHER BOARDS

WRITE

r !

READ

PROCESSOR BOARD

ADDRESS
DECODER

MEMORY BOARD

Fig. 4. A bidirectional bus system using Tri-state bus transceivers. On the processor board the trans-
ceivers are used as bidirectional bus buffers; on the memory board as an interface between a bidirec-
tional bus and two unidirectional buses. (Only one of eight lines of the data bus is shown.)

tails is beyond the scope of this
article.

For all buses, however, no
matter what their purpose, one
important rule always holds:

Only one device may talk at one
time. In that respect conversa-
tions between the circuit
boards in a computer are not
different from conversations

between people: If more than
one talker tries to speak at the
same time, the listener— be it
human or microprocessor — can
become utterly confused. ■

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Lucas' Puzzle

Here's a little puzzle/program that you should find interesting, n'est-ce pas?

This puzzle was invented
in the late nineteenth
century by a French mathe-
matician named Edouard
Lucas, hence it s name. It is
one of a group of games
whose object is to reverse a
given pattern. Generally the
pattern is formed by colored
pegs placed in holes in a

board. This game is one of
the simplest of this type.

First, a marker (in the
program the markers are
asterisks or the letter X) may
only be moved into the
empty space. There are two
ways to do this: either slide
the marker into the adjacent
empty space or jump a mark-

er over another marker into
the space. Second, asterisk
markers move only to the
right; X markers move only
to the left.

To make a move simply
enter the number above the
marker to be moved, a
comma and the number
above the space. You win

when all the X markers have
been moved to the left end
and all the asterisks to the
right leaving a space (shown
by an O) in the middle.

The puzzle can be solved
in 24 moves, but it can get
quite tricky; it's easy to get
into a position that's impos-
sible to get out of. ■

10INPUT"INSTRUCTIONS?",I$

20 IF l$(1,1)="Y"THEN GOSUB 500

30 DIM B(9)

40 FOR 1 = 1 TO 4

50 LET B(l)=1

60 NEXT I

70 LET B(5)=0

80 FOR l=6T0 9

90 LET B(l)=10

100 NEXT I

110 LETM=0

120 PRINT'THE BOARD AFTER MOVE"M

130 PRINT""

140 PRINT ""

150 PRINT" 1 23456789"

160 PRINT ""

170 FOR 1 = 1 TO 9

180 IF B(l)=0THEN PRINT" 0";

190 IF B(l)=1 THEN PRINT" * ";

200 IF B(I) = 10THEN PRINT" X ";

210 NEXT I

220 PRINT ""

230 PRINT ""

240 INPUT "YOUR MOVE?",X,Y

250 IF X=99 THEN GOTO 760

260 GOSUB 350

270 IF F=1 THEN GOTO 240

280LETB(Y)=B(X)

290 LET B(X)=0

300 FOR 1=1 TO 4

310 IF B(I)<>10THEN EXIT 340

320 NEXT I

330 IF B(5)=0 THEN GOTO 770

340 GOTO 110

350 LETF=0

360 IF B(Y) OOTHEN GOTO 470

370 IF B(X) = 10THEN GOTO 440

380 IF B(X) = 1 THEN GOTO 410

390 IF B(X)=0 THEN GOTO 470

400 GOTO 470

410 IF X >=Y THEN GOTO 470

420 IF Y-X>2THENGOTO 470

430 RETURN

440 IF X <=Y THEN GOTO 470

450 IF X-Y > 2 THEN GOTO 470

460 RETURN

470 PRINT"|LLEGAL MOVE. REENTER."

480 LET F=1

490 RETURN

500 PRINT "" : PRINT ""

510 PRINT" LUCAS' PROBLEM"

520 PRINT "" : PRINT ""

530 PRINT'THE OBJECT OF THIS GAME IS TO"

540 PRINT"EXCHANGE THE POSITIONS OF THE "

550 PRINT"TWO SETS OF MARKERS; * AND X"

560 PRINT"TO DO THIS YOU MUST MOVE THEM"

570 PRINT"INTO THE SPACE MARKED WITH AN"

580 PRINT" '0'. THE MARKERS MAY BE MOVED"

590 PRINT"EITHER INTO THE '0' SPACE"

600 PRINT"IF IT IS ADJACENT OR A SINGLE"

610 PRINT"MAKER MAY BE JUMPED."

620 PRINT'THE '*' MARKERS MOVE ONLY"

630 PRINT'TO THE RIGHT AND THE 'X' ONES"

635 PRINT"ONLY TO THE LEFT."

640 PRINT ""

650 INPUT"RETURN TO CONTINUE.", I$

670 PRINT"" : PRINT"A MOVE IS MADE BY ENTERING THE"

680 PRINT"NUMBER ABOVE THE MARKER TO BE MOVED"

690 PRINT"AND THE NUMBER OF THE SPACE"

700 PRINT'TO WHICH IT IS TO BE"

710 PRINT"MOVED. THE PUZZLE CAN BE SOLVED"

720 PRINT"IN 24 MOVES."

730 PRINT ""

740 INPUT "RETURN TO PLAY.",I$

750 RETURN

760 END

770 PRINT"CONGRATULATIONS, YOU DID IT."
780 END

Program listing.

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Home Brewing in Style

In computing's construction kitchen, why don't you give solder less
breadboarding a try in your next recipe.

The breadboard in use, showing a portion of an 8-bit parallel interface
for a high-speed paper-tape reader.

One area of hobby com-
puting badly in need of
development is that of tools
and gadgets designed to make
life easier for the hardware
home brewer. Pretty boxes
and single-board computers
dominate the market to such
an extent that home brewing
hardly seems worth it. Now
don't get me wrong — there's
a lot to be said for those
pretty boxes; I own one
myself. They just don't lend
themselves too well to home
brewing.

Sure, there are a lot of
prototype (mostly wire wrap)
cards available for Altair bus
systems and others. But I

100

don't relish the idea of
wrapping and unwrapping a
bunch of connections on a
board sticking out of the top
of my Altair during the
course of developing a
particular interface or periph-
eral circuit.

It just so happens that
there is a better way — the
use of "solderless bread-
board" sockets. The principle
of the solderless breadboard
is simplicity itself. An array
of contacts is held in a
molded nylon block full of
holes on .1 inch centers, the
standard lead spacing for
most DIP ICs. These contacts
are bused together to provide

numerous isolated multicon-
tact tie points. The contacts
are designed to accommodate
such things as IC pins, dis-
crete component leads, or
22-gauge solid hookup wire.
One simply inserts the desired
component or lead in a hole,
and the springy metal contact
material grabs it, insuring a
physically secure electrical
connection.

Breadboarding

I would guess that most
computer hobbyists have seen
the Bugbooks ... a kind of
lab workbook on micro-
computers. The companion
to the series is an 8080
system incorporating its own
integral breadboard. No
hidden stuff going on inside a
pretty box there; it's all hang-
ing out in the open! This was
my inspiration for a better
computer prototyping con-
figuration. Since I already
had a computer and wasn't
about to buy another one,
my goal was to bring the
breadboard to my existing
system.

When I first began design-
ing add-ons for my Altair, I
tried using a general-purpose
logic prototyping system
(built around a pair of solder-
less breadboards) that I had
devised several years ago. It
afforded me plenty of flexi-
bility and room for the

simple circuitry I was
developing, but before long I
was having to contend with a
mess of wires running
between the computer and
the breadboard. Any circuit
handling parallel data, sync
and status lines, etc., can
rapidly develop into an un-
manageable tangle.

After studying the prob-
lem for a while, I realized
that one thing I had going for
me was that the Altair uses a
standardized connector for all
I/O. So at least I could make
up a standard set of inter-
connect cables for bread-
boarding. Still, there was the
problem of how to get all
those lines neatly on and off
the board.

Fortunately, I had had
previous experience with an
E&L Instruments product,
the BP-22 solderless turret
terminal. It provides the same
type of individual solderless
connections as the bread-
board. On the completed pro-
totyping system, two sets of
25 of these terminals allow
me to selectively make easy
connections to two pairs of
DB-25 connectors. Each pair
consists of a plug and a
socket with like pin numbers
wired together. This arrange-
ment affords me a degree of
flexibility of interconnection
and has proved itself most
useful in the design of circuits
that connect the computer
and an external device. Addi-
tional turret terminals wired
to color-coded binding posts
provide for power-supply
connections.

A 17 x 8 x 2 inch alumi-
num chassis serves as a base
for the system. Although I
have thus far found two
solderless breadboards to be
adequate, the chassis is laid
out in such a way as to
permit the addition of two
more. Except for the wiring
between the turret terminals
and connectors, the underside
of the chassis is empty. There
is plenty of room for power
supplies, pulse generators, or
whatever; I elected to keep
the whole thing as simple and
as passive as possible.

A word about bringing bus

lines out of the computer
cabinet is in order. Don't
indiscriminately wire bus
signal lines to a rear-panel
connector. Unless they are
properly terminated, bringing
such lines out of the cabinet
will usually result in the
introduction of extraneous
noise on the bus, and we all
know what that means —
trouble. Since different
system buses have different
electrical characteristics, bus
termination techniques will
vary from machine to ma-
chine. It would be best to
contact the manufacturer of
your computer for his recom-
mendations.

Precautions to Follow in
Breadboard Use

Regarding the use of the
breadboard itself, there are a
few precautions that one

should observe. First, people
tend to get rather sloppy
when using a solderless bread-
board. Connections are made
so easily and quickly that it
lakes a conscious effort to
prevent the thing from look-
ing like a convention of
spiders. Believe me, though,
the time taken to lay out a
circuit neatly is well spent,
resulting in a saving of grief
and headaches during the
troubleshooting phase of the
design process. One of the
best ways to insure neatness
is to plan the layout before
you begin. It also helps to
keep an ample supply of
various lengths of pre-
stripped color-coded number-
22 solid hookup wire handy.
The second thing to
remember is that a bread-
board — any breadboard — is
going to be more noise prone

Top and bottom views of the "solderless breadboard.
view clearly shows the contact busing arrangement.

The bottom

than a PC card design. This is
particularly true of TTL
circuitry handling fast rise-
time signals. So use lots of
bypass capacitors.

Finally, we all do make

mistakes. Invest in some fire
insurance — be certain that
the power supply you use to
feed the breadboard is short-
circuit protected and current
limited! ■

The solderless turret terminal prior to installation.

Detail of several solderless turret terminals mounted and in use.

, x » « 4 * 1 *»'•/<»* >*
>f * «» i» * 1 t* *i U %i t0 u

«.. «. *• m «»-

*«* n * * » *i i* u m* •*

■ami

• 1

W WW

mmm

Top view of computer prototyping breadboard system.

Bottom view of computer prototyping breadboard system.

101

NOW A SOLUTION
TO YOUR I/O HEADACHE # 33

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it has a scroll up feature and full X-Y
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the price is only $275.00 in kit or
$350.00 assembled, plus S3.00
shipping and handling. To order phone
or write.

OTTO ELECTRONICS

P.O. Box 30BB
Princeton, N.J. 08540

609/448-91 65
Dealer Inquiries Invited

MC, BAC, COD accepted N.J. residents add 5°/o sales tax.

PHYSJCTOS

fflCRQCaiaRJTER
CLUB

• FREE Medical and Business
Microcomputer software

• Coverage of Regional Medical
Society Computer Conferences.

• Articles by Physicians on the use
of Microcomputers in their prac-
tices and research.

• Special Club discounts on Micro-
computer equipment and system
programs.

• Hobby uses of microcomputers
for Investment Analysis, Games,
and Education.

• National coordination of infor-
mation and activities involving
the use of Computers in
Medicine.

THE PHYSICIANS
MICROCOMPUTER REPORT

Don't miss another issue of our monthly magazine.

If you are interested in Microcomputers for hobby
use, for Medical applications data processing, or
for handling your professional business needs;
The Physicians Microcomputer Report will help
you.

The computer is an extension of your own mind.

Our magazine will give you the knowledge that you
need to understand, purchase, and use microcom-
puters in your office, home, and research.

View the Medicine of the future.

We publish FREE computer programs that will
help you improve your professional operation.
Now is the time to discover what microcomputer
technology can do for you, and to learn how other
Physicians are using their own personal com-
puters.

Please start my Club Membership and Subscription to the Physicians Microcomputer Report.

Name (Print)

City

Address

_ State _

Q $25 One year (12 issues)
D Bill Visa/BankAmericard

Credit Card #

Expir. Date

Zip.

□ $15 Special six month trial subscription
D Bill Master Charge
Interbank #

DRM-478

Check enclosed for $

Send to: Dr. Gerald M. Orosz, Editor, Physicians Microcomputer Rsport,

Box 6483, Lawrencevllle, N.J. 08648
Credit Card Customers can call
for quick ssrvlca: 1 -609-989-931 3

102

DISK ASSEMBLER

and
DISK EDITOR

Both programs read and write disk files; file size not
limited by memory. Assembler will assemble up to
ten source files at a time; permits modular pro-
gramming with programs easily relocated by
reassembling at the desired address. Editor does
not use line numbers; it searches for strings. Lines
may be inserted, deleted and displayed. Large disk
source files allow programs to be fully commented.

ASSEMBLER/EDITOR on disk
with users manual. ..$30

COMPUTER SYSTEMS DESIGN

906 N. Main Wichita, KS 67214

DEALERS INQUIRIES INVITED

Don Lancaster's ingenius design provides software
controllable options including:

• Scrolling • Full performance cursor

• Over 2K on-screen characters with only

3MHz bandwidth

• Variety of line/character formats including
16/32, 16/64 ....even 32/64

• User selectable line lengths

TELL ME MORE! ( ) Send instruction manual for the TVT-6 Kit '

with full operational details. $1 enclosed. *
( ) SEND FREE CATALOG

pg Name: . •

Address:

State:

Zip:

ELECTRONICS, INC. Ci *

DEPT.6-K . 1020W.WILSHIRE BLVD.. OKLAHOMA CITY. OK 73116

8K
BASIC

for
KIM-1

The famous high speed Microsoft BASIC
is now available for KIM-1. The 9-digit
accuracy version is available on cassette or
paper tape.

DEL I VER Y FROM S TOCK.

$99.00

$2.00 shipping and handling

IOHNOI

COMPUTER

P.O. BOX 523
MEDINA, OHIO 44256

LOW LOW COST

S-100 BUS MICRO-COMPUTER HEAVY CURRENT

POWER SUPPLY KITS

KIT A: $57.50

3 Hour Assembly Time -Complete Instructions Included

DIMENSIONS OF KIT: I3"(D x 5"(w) x 4 7/8"(h)

4 Unregulated Voltages Available
+ 8.5V/25A, -8.5V/3A, + 17V/3A

Includes TRANSFORMER T 2 [25A, size 3/ 3 /4" (I) x 4Vb" (w) x
3 1 /e" (h)], CAPACITOR C«| (100,000 UF, 15V), BRIDGE RECTI-
FIERS: D«| (30A, 50V) & D 2 (4A, 50V), FUSE HOLDER,
BARRIER STRIP, ALUMINUM PLATE [13"(l) x 5"(w) x 3/16
(t)], 3X CAPACITORS (6,000 UF, 45 V), 4X RESISTORS and
All Necessary Mounting Parts.

4 Unregulated Voltages Available
+8.5V/15A, -8.5V/2A, ±17V/2A

All Parts are same as in KIT A, EXCEPT: CAPACITOR Ci
(52,000 UF, 15V) and TRANSFORMER T«| [15A, Size 3 3 /a" (I) x
4" (w) x 2 13/16" (h)].

KITE: $47.50

(216) 725-4560

You May Buy Transformers Alone:

T 2 (25A) & Ti (15A) at $22.50 and $17.50 respectively.

SHIPPING CHARGES: $4.75 per TRANSFORMER
FOR EACH KIT: $5.00 in California. $7.00 for all other States.
California Residents add 6% sales tax.
Master Charge & BankAmericard. OEM Available

SUNNY INTERNATIONAL s 65

Mail Order Store

P.O. Box 4296 7245 E. Alondra Blvd.

Torrance, CA 905 10 Paramount, CA 90723

(2 13) 530-3732 Mon.-Sat.: 9 am-6 pm

103

Wasatch delivers quality system components from stock

4K x 8 RAM
2K/4K x 8 PROM
8-SLOT MOTHER
80 LINE DIGITAL I/O

Assem. /Tested

$89.95

50.00

Kit

$79.95
79.95/129.95
40.00
59.95

PCB

$22.50
22.50
2000
20.00

New 5V system components under development

• 8K x 8 EPROM (2716)

• 16/32 Channel, 8 Bit A-D

• 4 Channel, 8 Bit DA

4K RAM

Wasatch also delivers prime semiconductor
memory at reasonable price, in addition tocus
torn design services W13

SEND CHECK OR MONEY ORDER

WASATCH SEMICONDUCTOR PRODUCTS

25 South 300 East • Suite 215 • Salt Lake City. Utah 841 1 1
For o rders under $25 . add $2 shipping & handling / Utah residents add 5 sales tax

JOHNSON -

COMPUTER p - O. BOX 523, MEDINA, OHIO 44256

■■■■■■^H (216) 725-4560

FINALLY!

HDE inc. FLEXIBLE DISK SYSTEM FOR KIM
Features:

*Top Quality Industrial Grade Controller
*Proven High Reliability Disc Drive
* Line-Numbered Text Entry and Editing
*A Powerful Command Structure
"Adaptation to any 6500 Based System
"Capability for User Defined Commands
"Complete Compatibility with KIM
"Multiple Resident Files

"Indexed and Non-Indexed Disk Storage

Complete 90 Day Parts and Labor Warranty

HDE FILE ORIENTATED DISK SYSTEM

'TODS"

Includes:

"Full Size Sykes Drive
"6502 Based Controller
"Power Supply
"FODS Software
"Cables, Interface Card
"User Manual

"your BASIC software magazine"

First Issue October!

Featuring:

• Programs in theTRS-80 Level II BASIC

Cribbage-A 16K masterpiece that's hard to beat
Calculator-Practical, useful and small enough to
fit anywhere

State Capitol Quiz-A teaching aid for youngsters
Death Star-You wear the black hat in this
simulation

• Software Tutorials
TRS-80 Programming Hints
TRS-80 Hotline
And much, much more

S66

Prepublication Offer

Order now and get the first 12 months of Softs ide
for just $10.00 (reg. subscription price $15.00). To
order mail check or money order to:

SoftSide Subscriptions

POBox68 Milford NH 03055

P.E.T. Food

NOURISH YOUR HUNGRY P.E.T. WITH SELECTIONS
FROM CREATIVE SOFTWARE'S EXTENSIVE MENU!

DUAL JOYSTICK INTERFACE: This Creative Software interface
allows you to plug in two Atari -type joysticks (not included) with no modifi-
cation to the P. E.T. Comes with two games and complete programming in-
structions $35.00

JOYSTICKS: for above interface, price each $1 2.50

BREAKOUT: Written in BASIC for the P.E.T., this program uses
either keyboard input or any Creative Software joystick (single or dual).
You get ten balls to knock out three double layers of bricks $10.00

LIFE: (By S. Bartonsmith) Possibly the finest personal computer version
of LIFE currently available, this program uses machine language routines
to display up to four new generations per second. User-definable initial
configuration, complete screen wraparound, and introducing two original
additions --"posts" and "holes." $20.00

TRAP and CRAPS (Joystick or keyboard input) $10.00

HURKLE and ONE-QUEEN (Joystick or keyboard input)... $10.00
HOUSEHOLD FINANCE Parts I and II $15.00

ORDERS: Send check, money order, or VI SA/Mastercharge (include
expiration date) and add the following shipping charges: 1 -2 programs (or
dual joystick interface)- 1. 50. 3-4 programs- 2. 00. 5 or more programs-
2.50. Extra joysticks, each- 1.50. California residents add 6% sales tax.

INFORMATION: More information on these and many other currently
available programs are available on a free flyer Write directly to Creative
Software for a complete list.

Creative Software

C97

P.O. BOX 4030, MOUNTAIN VIEW, CA 94040

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105

Datapoint CRT Terminals

Fully-Assembled — Guaranteed

#3000 $595.00 #3360 $649 . 50

refurbished

Add $15.00 Packing
Terms Check or MO
Guaranteed 90 days

Shipped FOB Washington, DC.
Immediate Shipment

MODEL 3000

25 lines x 72 characters, Full or half duplex speeds 1 10, 150, 300 Baud, higher
on options

MODEL 3360

25 lines x 82 characters (Scrolling version 24 lines); Supplied either
DATASHARE compatible, or scrolling, add $3500. Addressable cursor Speeds
300, 1 200, 2400, 4800 Baud, higher on options. Block transmit standard. Extra
buffer, external item control capability on options.

Both terminals have Standard ASCII reed-switch keyboard with any-key
rollover, user-codeable keyboard matrix, numeric keypad, cursor control keys,
green P-31 screen phosphor, standard RS-232 interface, Printer output. Up to 2
Amps at 5, 14, 25 volts available to drive KIM-I or other small processor
Manual $10, Cable kit $9.95.

M-33 KSR Teletype $495.00. Other printers, drives, available, also Datapoint
2200.

We can service CRTs, micros, main-frames. Quantity discounts available.

TELECOMMUNICATIONS SERVICES CO.

Box 41 17, Alexandria, Va. 22303
703-683-4019 / TLX 89-623

T26

Radio Shack Computer Users

TRS-80

monthly
newsletter

The largest publication devoted to the TRS-80 System

• Business • Software Exchange

• Personal Finance • Market Place

• Practical Applications • Questions and Answers

• Gambling — Games • Program Printouts

• Latest RADIO SHACK Developments

• . . . and more

Major programs published monthly . . . Complete income tax
program (long and short forms) . . . Inventory control ... Ex-
tensive mailing list and file program . . . Payroll . . . Stock
selection and indicators . . . Horse selector for picking win-
ners . . . Renumber program lines . . . Chess . . . Checkers . . .
Financial package . . .

S24- Per Year

Box 149K New City, New York 10956 (914) 425-1535

Send for FREE Software Catalogue (Including listings of
hundreds of TRS programs available on cassette and diskette).

Output from
Instant Software Inc.

by Sherry S my the

We did it! An impossible (sometimes) dream come true .... first royalty checks went out
the first written was over $500! Looks like there might be some $1000 checks with the next
batch .... all this without the heavy advertising that will occur when our software library is
more extensive.

You, too, can get a piece of the action .... if you can write good programs and document
them, that is.

It's easy if you set your mind to it ... . gather together your best programs, put them on
cassette, prepare your documentation carefully, submit them to INSTANT SOFTWARE, INC.,
then sit back and before long you'll be taking royalty checks to the bank.

The biggest slowdown in the publication-of-software biz is the lack of good documentation.
You wrote your program, you know better than anyone else what it does and how it is better
and/or different from another of the same subject matter .... this is part of what you want to
include in your documentation. Documentation should be submitted in the same format as
articles: typed on one side of page, double-spaced with wide margins, typed in uppercase and
lowercase letters and written to be understood by a person with little or no computer
background. . . . The buyer shouldn't have to do any real thinking as far as running the program
. . . for games, rules that aren't on the actual program as it appears on the screen should be
included in the documentation booklet .... for old "standards" such as chess and checkers,
detailed rules are not necessary .... but any changes you've made to get the "standards" to run
should be explained in detail.

The easier it is for the purchaser to use your program, the better he will like it and use it ... .
his good vibes will pass to others and your royalty checks will increase by the month.

We are tentatively scheduling for production the following mix as far as brands of computers
go: For each five published programs (one-a-day per week schedule) there will be two TRS-80,
one PET, one Apple and one of the "others." We'll try to keep a mixture of topics going ....
business programs will get first priority.

We are very receptive to any and all suggestions about improving our product and services.
Write to INSTANT SOFTWARE, INC., Department S, Peterborough NH 03458, USA.

INSTANT SOFTWARE

a product of 1001001 inc. Peterborough, nh 03458

KIM-1 EXPANSION

K I M-4 Motherboard $119.00
8K Static RAM $195.00
8K PROM Board $195.00
64 Character/ line Video $149.00

KIMSI S-100 Motherboard $165.00
8K Static RAM $197.00
32K Static RAM $599.00
64 Character/ line Video $149.00

KEM S-100 Motherboard $155.00
includes sockets for 4K 2708 on board
64 Character/line Video Module $255.00
8K Static RAM $197.50
32K Static RAM $599.00

HDE Floppy Disk

PROM Programmers

All items are available from stock.

JOHNSON

COMPUTER

P.O. BOX 523
MEDINA, OHIO 44256

(216) 725-4560

106

HARDWARE 6800

SS50/SWPTC

QUAD D/A CONVERTER SYSTEM

4 High Speed DACs Plus Z-Axis Output for Graphics

Assembled and Tested $195 00

EIGHT CHANNEL A/D SYSTEM

• Low Cost • High Performance • Analog Data Acquisition

Interface
Assembled and Tested 125 00

SERIAL COMMUNICATIONS INTERFACE

• Full RS232 I/O • Modem Control Signals • Prototype Area
Assembled and Tested 50 00

MULTIPROGRAMMING OS/CONSOLE MONITOR ROM

Mikbug* Compatible • Multiple ACIA or PIA I/O

RT/68 (6830 or 2708 package) + 80P Systems Manual 55 00

MEK 6800D2

D2 KIT' UPGRADE PACKAGE
Converts D2 to Terminal I/O • Compatible with
popular software: BASIC, assemblers, etc.
Includes RT68. RS232 Interface + 100P Manual 75.00

SOFTWARE

A/BASIC 6800 COMPILER

• GENERATES FAST EFFICIENT MACHINE CODE

• NO RUN TIME PACKAGE REQUIRED

• SUPPORTS MULTIPROGRAMMING

A/BASIC V2 0D 12K DISK EXTENDED (MINIFLOPPY-S S B

DOS or FLEX)

A/BASIC V1 0C 8K CASSETTE-ORIENTED* on K C CASSETTE

"(Cassette version requires RT/68)

CHESS V1.0

6800 CHESS VERSION 10

Challenging 8K Chess Game • Source + Object

Minifloppy or Cassette

ARTIFICIAL INTELLIGENCE DEMO

ELIZA VERSION 10

6800 as Psychoanalyst • Source ♦ Object

Minifloppy or Cassette

$150 00
5000

Phone orders accepted. Write or call today for complete information and our free catalog.

MICROW\RE SYSTEMS CORPORATION

MASTERCHARGE

PO. BOX 954 • DES MOINES, IOWA 50304 • (515) 265-6121

'MOTOROLA TRADEMARK

M60

BANKAMERICARD

SURPLUS ELECTRONICS

ASCII

IBMSELECTRIC
BASED I/O TERMINAL
WITH ASCII CONVERSION
INSTALLED $645.00

• Tape Drives • Cable

• Cassette Drives • Wire

• Power Supplies 12 V1 5 A, 12V25A,
5V35A Others, • Displays

• Cabinets • XFMRS • Heat
Sinks • Printers • Components

Many other items
Write for free catalog
WORLDWIDE ELECT. INC. W16
130 Northeastern Blvd.
Nashua, NH 03060
Phone orders accepted using VISA
or MC. Toll Free 1-800-258-1036
In N.H. 603-885-3705

X AND Y

P LOTT E R

IEEE -488 INTERFACE

IFOR THE DC TOR HP.
I BUSS rE ■ USER

FROM TTL PORT
DIRECT TO PLOTTER

'Vfe

I DIGITAL STEP RESOLUTION OI5
> ALPHA - NUMERIC SOFTWARE

KIT IS $195,-
ASSEMBLED- TESTED $ 249,

X & Yx- %*

X2 Cfifo,

ENTERPRISES *fo' C *

P.O. BOX 796

HUNTSVILLE.AL. 35804

D.C. METRO AREA

TYSONS CORNER. VIRGINIA
THE

COMPUTER SYSTEMS
STORE

MICROCOMPUTERS & PERIPHERALS
HOME. SCHOOL & SMALL BUSINESS

FEATURING

Small Business Systems Complete with

Application Software Including

Word Processing

DEALERS FOR

Commodore Pet
Processor Technology
Polymorphc
Cromemco
Southwest Technical
Micro-Computer
Business Systems, inc

Lear Siegtef
Diablo

Texas Instruments
DEC

North Star
Anderson Jacobson
Books & Magazines

CSS

1 984 Cham Bridge Rd
McLean. VA

703-821 -8333

C73

KIM-1 ™ ACCESSORIES FROM MTU

U
Hill

VISIBLE MEMORY
Graphic Display K 1008

• 320 wide 200 high bit mapped graphics

• 8K byte onboard refresh memory

• Use as display, memory expansion, or both!

• Graphics and text display software available

• Direct KIM interface, no external logic needed

• KIM memory expansion signals provided

• Can use with other 6502/6800 systems <&
1.0MHz

• No wait states, no snow, and no processor
overhead to refresh display

• 75 ohm standard video 1.2V P-P (non-interlace)

• Low power: +8 (a 25A, +16 f 25A un-
regulated

• Assembled & tested $289.00. bare board
$40.00

• Graphics subroutine pack & demo program
$20.00

CARD FILE WITH
MOTHERBOARD K 1005

• Expansion boards fit under the KIM

• KIM and 4 expansion boards require no more
table space than the KIM alone

• Only the KIM is exposed

• All expansion boards are protected

• KIM and expansion boards rigidly supported

• Unbuffered KIM bus is well shielded

• 5 slots and backplane are preassembled

• KIM application connector also prewired

• Power input via 5 point terminal strip

• Chromated aluminum & glass epoxy con-
struction

• Assembled and tested $68.00

ill!* 1

fill*

16K MEMORY
K-1016

• 16K memory address-
able on any 4K boundary

• KIM-bus direct connec-
tion

• Transparent refresh

• Low power requirements
+ 8 V @ 0.2 Amps, + 16
V @ 0.2 Amps

• KIM memory expansion

signals provided

• Can use with other 6502/
6800 1.0 MHz processors

• Assembled & tested (5
day burn in) $375, bare
board $40

8 BIT AUDIO SYSTEM
K 1002

• D/A converter, 8 bits

• 3 5 kHz LP filter, 6 pole

• Audio power amplifier, 100MW

• Connects to 8 bit port

• Fantastic music software (KIM)
4 Voice harmony

Fourier derived waveforms
Different wave per voice
Music compiler & interpreter

• Speech synthesis possible

• Assembled & tested $35 00

• Software pack/cassette $13.00

Micro Technology Unlimited

P.O. Box 4596
29 Mead Street

Manchester NM
03108 .,

107

Thomas E. Hutchinson
35 War render Ave. Apt. 208
Islington, Ontario M9B5Z5
Canada

fit

ify Your COSMAC Elf

This modification to the Elf involves a lilliputian outlay of cash.

The COSMAC Elf micro-
computer described in
Popular Electronics (August
and September 1976) has

been one of the most inter-
esting projects I've built.
However, soon after wiring it
together and running a few

TO RESET KEY

♦5V

programs, it was obvious that
I spent a lot of time loading
programs by the eight front-
panel toggle switches. And
the frustrating part occurred
when I would make an error
at step 200, for example, and
the only way to get back to
that step was to press the In
button 199 times and then
make the correction. In sub-
sequent issues of Popular
Electronics, programs to
interface the microcomputer
with a keyboard and allow
the machine to jump to a
requested memory location
to make a correction there
were published. After looking
over these programs, I de-
cided they were not for me.

♦5V

r)^J

Tr*

ICI2A
CD4098

Tr-

RESET

CXOImF iook

♦5V

•A

Tr»

ICI2B
CD4098

-TL

First, you have to enter
them using the eight front-
panel toggle switches at the
beginning of every program,
which takes about 10 or 15
minutes every time you turn
the computer on. Second,
this program takes up valu-
able memory space; in fact, it
uses 74 of the 256 available
bytes in the memory. If you
want to expand your mem-
ory, the latter may not con-
cern you as much. Con-
sequently, I devised the
following circuit that inter-
faces a keyboard with the
microcomputer and also
allows you to jump to any
desired memory location very
quickly. The circuit requires
no programming and uses no
memory space.

Construction

The circuit was construct-
ed on a 4 x 8 x 2 inch
aluminum chassis. The chassis
is turned upside down (open
side up), and a piece of perf-
board with a grid of 0.05 x
0.05 inch mounts over the
open side using sheet metal
screws; a second piece of
perf board with a 0.1 x 0.1
inch grid mounts inside the
chassis. The hexadecimal
keyboard was purchased from
James Electronics, and the
spacing of the pins conforms
more or less to the 0.05 inch
grid. A few extra holes had to
be drilled to make it fit
exactly into the perfboard.
ICs 1,2,3,4 and 10 mount on
the top perfboard with the

♦5V

RESET
(RESET* I MAKES 5* I)

39K

■VAr

4,10

6,7,8

A
CLOCK
D 6

IC9
C040I3

Tr-

RESET

22mS

CLOCK
B O

TO PIN 13
ICI8 AND
♦ TO PIN 5
IC5

FIRST KEY PRESSED

SECOND KEY PRESSED

ICIIC
IIC04OM

PIN 5IC6
PIN 6 ICI7
PIN 3 ICI8
PIN 6IC20

ImS

DEBOUNCE
KEYBOARD

108

Fig. 1. Keyboard encoders and latches.

Fig. 2. Debounce and strobe circuits.

♦5V

PIN 2 IC5

CLOCK

ICI6
CD4520

ENABLE
R

•3

I s )

R
CLOCK

IC 16
CD4520

ENABLE

TO RESET KEY

♦5V

TO PIN I
ICI7

HIGH WHILE L0W WHEN
COUNTING C0UNT |S

REACHED OR
WHEN RESET IS
PRESSED

FROM PIN 3.ICI9

COUNTERS

GATES COMPARE OUTPUT OF COUNTERS
WITH OUTPUT OF IC5 AND IC6

Fig. 3. Counter and compare circuits.

keyboard; the remaining ICs
mount on the second pert-
board. IC sockets were used
throughout, and wiring was
accomplished by working
several evenings using a
Vector wiring pencil. The
keyboard has several
uncommited keys, one of
which you must designate as
a reset.

Circuit Description

ICs 1, 2, 3, 4 (Fig. 1)
produce the proper code for
each key pressed; e.g., when
D is pressed you get 1101.
IC10 detects the closure of
any key, and its output is
inverted by IC11A, which
feeds a debouncing circuit
made up of the two mono-
stable multivibrators in IC12.
IC12A (Fig. 2) triggers on the
rising edge of the input,
sending out a 22 ms pulse.
Assuming that all contact
bounce is over in less than 22
ms, IC12B will trigger on the
falling edge of this 22 ms
pulse and send out a 1 ms
pulse. When the key is re-
leased, IC12A may or may
not generate another 22 ms
pulse, depending on how bad
the key bounce is. IC12B will
not be triggered by this pulse
because triggering occurs only
on the falling edge, which

does not occur until 22 ms
after the key has been re-
leased. The moment the key
is released, the low signal on
the reset of IC12B prevents
triggering. In summary, IC12
generates a single 1 ms pulse
for each keystroke.

IC11B produces a 1 ms
pulse on the first keystroke
that gates the outputs of ICs
1, 2, 3, 4 into IC5, which
then stores the binary code
for the first key. IC11C pro-
duces a 1 ms pulse on the
second keystroke that gates
the outputs of IC1, 2, 3, 4
into IC6, which then stores
the binary code for the
second key. At the same
time, this pulse goes to pin 3
of IC18, which inverts the
pulse and signals COSMAC
that the data is ready to go

Right: The COSMAC Elf. Center: Keyboard support circuitry with top
removed and shown at the left.

into memory. The pulse is
not synchronized to
COSMAC's internal timing,
but it lasts much longer than
a timing cycle, guaranteeing
that the memory will get the
data. The third and fourth
keystrokes behave like the
first and second, a pulse going
out after the fourth to signal
that the data is ready again.
The whole operation is fully
automatic, and there is never
any need to press the input
button. IC7 and IC8 are
buffers required to drive the
COSMAC circuitry.

Figs. 3 and 4 show the
circuit I devised to advance to
any desired step in the pro-
gram. In effect, all these
circuits do is push the input
button the required number
of times to get to whatever
program step you enter on
the keyboard. For example,
you want to go to step OB —
so you press reset, set mem-
ory protect, reset COSMAC

with the load switch and
enter OB. IC19 will send out
12 pulses, which, through
IC18, advance to step OB.
IC19 oscillates at 1000 Hz, so
the time to get to the last
step in the program, FF, is
about 256 ms. All other steps
will be reached in less time.
IC19 drives the first four-
stage binary counter in IC16,
and the output of this
counter drives the second
one. Together these can
count to any desired value
from 00 to FF, and their
outputs are in binary form.
Let's say you enter B7 on the
keyboard. IC19 starts oscil-
lating and I CI 6 starts
counting the pulses. IC14 and
IC15 compare the output of
the counters to the B7 stored
in IC5 and IC6; when the
counters get to B7 a signal is
sent out via IC1 3, IC1 1 D and
IC17 to stop IC19. IC19
sends out exactly 183 pulses,
and assuming COSMAC was

♦ 5V

FROM PIN 4
ICIID (STOP
OSC )

X I0K I

FROM PIN IO

IC 1 1 (START OSC)

GOES TO ZERO TO
STOP OSCILLATOR

TO PIN 12
(CIS

TO PIN IO
ICI6

LATCH

GATED
OSCILLATOR

Fig. 4. Oscillator circuit.

109

22K

►5V

♦5V

INPUT BUTTON
ON COSMAC

FROM PIN 10
ICII

FROM PIN 9
ICI6

DPDT SWITCH REPLACES
SPDT SWITCH IN COSMAC

-NORMAL

MEMORY PROTECT

_ NORMAL

MEMORY
AOVANCE

FROM PIN II »
ICII

FIRST KEY PRESSED

SECOND KEY PRESSED

CD4023

in__n_TLn n_n_

)

T0ICI2

ICII
CD40II

REMOVE THIS
WIRE WHEN
INSTALLING
KEYBOARD
SYSTEM

COSMAC

Fig. 5. COSMAC interface.

at step 00 initially, you
would arrive precisely at step
B7. In Fig. 5 it will be
noticed that at pin 10 of
IC18 you get one extra pulse
from the first keystroke. This
is needed to set the program
back to step 00, and it elim-
inates the need to press the
input button.

Fig. 6 shows an optional
circuit that provides an
audible beep on every second
keystroke. The reason for
including this is that some-
times when your are entering
a lengthy program you will
strike a key, but not press it
hard enough to actually make
the contact. You go on your
merry way, not realizing your
mistake because you haven't
been looking at your hex

display. You end up having
the last digit of each entry
paired with the first digit of
the following entry. It's quite
a mess, believe me!

IC20 is a dual timer, the
first half of which stretches
that 1 ms pulse into a 25 ms
pulse. The second half is
connected as an astable multi-
vibrator driving a loud-
speaker. It is gated on for 25
ms and gives a beep. A 68 uF
capacitor and 220 Ohm re-
sistor decouple this circuit
from the 5 volt line and
reduce current consumption.
If a longer beep is desired,
increase the 0.22 uF capa-
citor. If a different pitch is
desired, change the 0.027 uF
capacitor. Any speaker will
probably do; I used a 2-inch

<\ 2 , 2 IOOK

imS

FROM PIN 10
ICII

220
• • w •

027

1. 2

IC20
LM556

•A

SPEAKER

MONOSTABLE

GATED OSCILLATOR

Fig. 6. Optional circuit to provide beep on every second keystroke.

one from Radio Shack.

Modification of COSMAC
Circuitry

The eight front-panel
switches must be discon-
nected. The outputs of IC7
and IC8 in Fig. 1 are con-
nected in their place. The
memory-protect switch must
be replaced with a DPDT
toggle switch, one-half of
which is wired up as in the
original, while the other half
is wired as shown in Fig. 5.
The input button is rewired
as shown and is denounced
by an unused part of IC8. As
shown, you must remove the
wire joining pins 9 and 12 of
IC11 in COSMAC.

Using the System

To enter data into mem-
ory, press reset, set COSMAC
to load and start using the
keyboard. To check what

you've entered at a particular
step set memory protect,
reset the load switch and
leave on load, press the reset
key and enter the step you
want to see on the keyboard.
You can then change the data
in the following step by just
switching off the memory
protect and keying in what-
ever you want.

The input button behaves
as it did in the original design,
and it can be used if the
program calls for it to be
pressed; or it can be used to
advance the memory one step
at a time.

Summary

The whole project cost me
around $55 here in Canada
where prices tend to be
higher. It has been worth
every penny in the increased
convenience and speed it pro-
vides in programming. ■

Canadian

8K MEMORY KITS

M1 — Fast Signetics 21L02-1 RAMs with 20
pages of Documentation— solder mask Low
power Schottky— S-100 Bus— Full Buffering

$179.95

M2— as above with DIP switch address select
and Robinson Nugent IC sockets only $199.95

MEM1— WAMECO bare board as used in
above kits $39.95

Write for info on WAMECO CPU and other
S-100 bare boards.

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We also stock Diablo 1345A (Hytype II*) mechanisms for immediate shipment at the
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129

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111

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INSTANT SOFTWARE

TRS-80

4K
LEVEL I

16K
LEVEL II

Space
Trek II

by KB1

0002R

"»1»nt So't««t« Inc P*t««DO*Owgr> NM 034M OS* ^* *.#»•• i,<t*- **»*

• SPACE TREK II- by KB1 (for the TRS-80TM)
This Space Trek game will challenge the most skillful and careful
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Order no 0002R.

INSTANT SOFTWARE

TRS-80

4K
LEVEL I

16K
LEVEL II

Basic and

Intermediate
Lunar Lander

by KB1

^.imuib «*» «' «•«* "■'»• warn

man

000 1 R instant Sot1w«re inc . Peterborough NH 03450 USA See reverse <o' piogtmrn mtotmmtto*

• BASIC LUNAR LANDER/INTER-
MEDIATE LUNAR LANDER by kbi (for

TRS-80TM) Your automatic landing system has malfunctioned and
you are forced to make a manual landing. Taking control at 15,000
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INSTANT SOFTWARE

TRS-80

4K
LEVEL I

16K
LEVEL II

Beginner's
Backgammon

by Fred Schild

and Keno

by KBi

0004R ln»i«nt Software Inc Peterborough NM 0)446 USA ** •••

• BEGINNER'S BACKG AMMON/KENO

—by Fred Schild and KB1 (for the TRS-80TM). You will never be in need
of a backgammon companion again! Schild's program is designed
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INSTANT SOFTWARE

TRS-80

4K
LEVEL I

16K
LEVEL II

by Wiltord Nieprascbk

Golf
Cross-Out

by David Dmehay

«<*'

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• GOLF/CROSS-OUT— by Wilford Niepraschk
and David Dillehay Playing golf on a computer? You bet and
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INSTANT SOFTWARE

TRS-80

4K
LEVEL I

16K
LEVEL II

Electronics I

Tuned Circuits & Coil Winding

555 Timer Circuits

LM 381 Pre Amp Design by Rick Morei

I nONOSTDBLC nULT!VIBR«TO» I

Tl* WlAY IS UK SCC.

CI IS . I *t'

Rl IS 4M545 WIS

" • CWCC1 HH 4

»i <«st; n

Pl« 6 <VCC

mt e rr* nun* wins - rot $ to iecf sm. v**,

0008R

0*l*'Ck>fough NM 034M USA

* O'og'a^ .«'<K*i«r«

• ELECTRONICS I by Rick Morel. With this group of
five programs you will be able to design coils for radio circuits,
calculate the component values for tuned circuits, design
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monostable or astable using the 555 timer IC.

Coils can be designed with the use of tables or special
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There is also a program for designing tuned circuits, audio or
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The LM-381 program draws the circuit diagram and gives you the
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These programs are not only helpful around any workshop or lab,
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INSTANT SOFTWARE

Ham
Package I

Basic Electronic Formulas
with Voltaga Dividar ■ , ■• . m. ..
Basic Electronic Formulas with
R/C Tim* Constant

TRS-80

4K
LEVEL I

16K
LEVEL II

Antennas ,

W BltCCTOB • 15.17 FT. ^

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This group of eight programs (we like to give you plenty) will be
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OHM'S LAW CALCULATIONS SERIES CAPACITANCES

FREQUENCY VS REACTANCE PARALLEL CAPACITANCES

SERIES RESISTANCES DIPOLE DESIGN

PARALLEL RESISTANCES YAGI DESIGN

These programs draw the circuits or antennas involved and let
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This series of programs is not only an excellent way to learn the
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they will also be of constant use in any workshop or hamshack
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Personal
Weight Control
and Biorhythms

by Microcosm

rtf>t>!t 19"8

li 3456 7896 Ii3«?6?89eti3«56?89ei

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Mortgage with
Prepayment
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by Microcosm

ENTER TMC PRINCIPAL AMOUNT
ENTER NORTGnGE 'ERH CVCMtt)
ENTER ANNU«L INTEREST RATE
NUMBER OF PAYMENTS PER VEAR

REGULAR PAYMENT
TOTAL TO BE PAID
COST OF THE MORTGAGE

IHM8.69

DO YOU WISH TO PREPAv YOUR MORTGAGE

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• PERSONAL WEIGHT CONTROL/

BIORHYTHMS— by Microcosm (for the PETTM) Here's
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CASINO I by Charles M. Stuart. There are blackjack

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INSTANT SOFTWARE

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Casino I

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Craps

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, . Mf . T£fc fc_,pc, ,

PmSS LINE
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IS THE P INT .
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Send me the following Instant Software:

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'Instant Micro Programs

Loop the Loop

What is a loop? How do you use it? The neophyte gets this
and other questions answered in this informative article.

James Gross

University of Wisconsin Center

Sheboygan Wl 53081

One of the most powerful
abilities of a digital com-
puter is to repeat a series of
program steps until a specific
condition occurs. This is called
iteration, or looping. We will
look at how loops can be used.
Examples will be given in
BASIC, but the principles apply
in any language.

In the paragraph above, a key
phrase is "until a specific
condition occurs." Otherwise,
you have a loop that repeats
forever. Home computing
systems usually have a BREAK
function, which can get you out
of a perpetual-loop condition,
or you can always halt the com-
puter completely. On a larger
commercial system, however,
these options aren't always
available. Most programmers
would agree that you should
avoid such "infinite loops."

To see the problems they can
cause, try the short program in
Example 1 (the idea comes
from an old joke).

It soon becomes evident that
the program is out of control!
What this program lacks to
have a controlled loop is, of
course, a terminating condi-
tion.

The simplest and most com-
mon technique in loops is a
numeric counter, or index, to
control the number of repeti-
tions. The index is set, usually
to value 1 , before the loop. After
the useful steps occur, the in-
dex is increased, or in-
cremented, by 1 and then
tested against the limit. (I will
use explicit incrementing and

testing to demonstrate the prin-
ciple, though all high-level pro-
gramming languages have
special instructions to ac-
complish these functions:
BASIC has FOR-NEXT, FOR-
TRAN has DO, and so on.)

As an illustration of the sim-
ple numeric index, suppose we
want to compute and print the
squares of the numbers one
through ten (see Example 2).
Lines 15 and 20 are the heart of
this program; the other lines
control the iteration. Line 10 ini-
tializes the index to 1, line 25 in-
crements it by 1, and line 30

tests for the terminating condi-
tion.

Note that because we want
the squares of 1 through 10,
and because we increment X
before the test, X will equal 10
in line 30 just after we've
printed the X = 9 answer. This
means one more cycle is need-
ed, computing and printing 10,
then making X equal 11, which
makes X< = 10 false, and end-
ing the program.

I have two additional com-
ments about Example 2. First, I
call it a one-shot program
because it always does the

5 REMARK EXAMPLE 1, INFINITE LOOP
10 PRINT "COMPUTERS ARE PERFECT. NOTHING CAN
15 PRINT "GO WRONG."
20 GOTO 15
25 END

Example 1.

5 REMARK EXAMPLE 2, SQUARES USING A COUNTER
10 LET X = 1
15 LET Y = X * X
20 PRINT X, Y
25 LET X = X + 1
30 IFX<= 10 THEN 15
35 END

Example 2.

6 PRINT "WHAT ENDING VALUE";

7 INPUT E

30 IFX<= E THEN 15

Example 2a.

5 REMARK EXAMPLE 3, TEMPERATURE CONVERSION
10 LET F = 90

15 LET C = INT (5 * (F - 32) / 9)
20 PRINT F, C
25 LET F = F - 5
30 IFF>= -40 THEN 15
35 END

Example 3.

same thing: If it runs a second
time, it produces a second copy
of the same table. In my opin-
ion, that's the function of a
photocopy machine, not a com-
puter. The program could easily
be made more flexible by modi-
fying it to take in a limiting
value (call it E for ENDING) and
comparing X with E. The
changes that would be made

are shown in Example 2a.

Now the program will com-
pute and print the squares of
values 1 through E. I'd like you
to try to make one more altera-
tion to generalize it fur-
ther — take in the starting value
also. Then if you need the
squares of values between
5126 and 5300, you don't have
to wade through the 5125 extra
lines of printout!

My second comment on this
program concerns the incre-
ment of + 1 we used. If your ap-
plication requires it, the incre-
ment can be negative, so that
the loop counts down instead
of up. A good example of this is
printing a Fahrenheit-to-Cel-
sius temperature conversion
chart (see Example 3) with the
Fahrenheit temperatures run-
ning down the left edge from
+ 90 to - 40 in 5 degree steps.
(A negative quantity added to a
counter is called a decrement.)

Note that the test in line 30
fails when F is less than -40;
that's what we want because
we're working downward. The
integer (INT) function in line 15
insures that the Celsius
temperatures are whole
numbers.

In the preceding examples,
the terminating condition has
been the value of the index, but
this doesn't have to be the
case. One common way of ter-
minating a loop containing an
INPUT or READ, for instance, is
to use a special target value
(also known as a trigger or sen-
tinel) whose only purpose is to
terminate the loop. It is useful
in cases where several input
data values must be processed,
but the exact number of them
isn't known. Let's see how this
works in an inches-to-centi-
meters conversion (see Exam-
ple 4).

This program will take in a
length in inches and print the

114

equivalent centimeter value,
repeating until a negative value
is entered. In the case of linear
measure, a negative value
makes no sense, and this
"illegal" condition is ideal to
use as a target. In applications
where either positive or
negative values can legitimate-
ly occur, the target value used
is either an extreme value
(temperature over 10000) or a
very unlikely value (length ex-
actly 999.9 inches).

In computer use, the greatest
impact of iteration is in calcula-
tions involving a so-called con-
vergence technique, in which
each cycle computes a closer
and closer approximation to a
desired value. A practical ap-
plication of this technique is
approximating the square root
of a number using the Newton-
Raphson method.

Suppose we're looking for
the square root of a value
named X. We begin by guessing
that the square root of X is a
value, G. Next, we compute the
quantity 1 /*(G + X/G). This
becomes the new value of G,
the computation is repeated to
get another G, then another,
and so on. Each G value will be
closer to the actual square root
of X than the previous G. The
loop can be made to terminate
when G squared is "close
enough" to X. The exact defini-
tion of close enough depends
on the problem and the specif-
ic computer's precision. Let's

5 REMARK EXAMPLE 4., METRIC LENGTH WITH TARGET VALUE
10 INPUT L
15 IF L<0THEN 35
20 LET M = L * 2.54
25 PRINT M
30 GO TO 10
35 END

Example 4.

work through a sequence by
hand to see this convergence
technique work.

Assume we want the square
root of 110. Ten squared is 100
and 11 2 is 121, which suggests
a value between 10 and 11.
However, to observe progress
toward the answer, let's make
our initial guess 25. Substitut-
ing X = 110 and G = 25 in the
formula, we compute a new G
(see Example 5). Using that new
G, we continue in Example 6.

In just four cycles, the square
root has been found.

Utilizing this technique in a
program, your initial guess can
be any nonzero value. In fact, it
can be the value whose square
root you're finding! (See Exam-
ple 7.)

Here, line 30 lets you watch
the value change. In a program
that used this technique, you
would probably just want to use
the answer. Line 35 repeats the
loop until the difference be-
tween successive guesses is
small. Asking this program to
find the square root of 110 (us-
ing 110 as the first guess) gives

G = Vi (25 + 110/25) = 14.7 Cycle 1

Example 5.

G = 1 /2 (14.7 + 110/14.7) = 11.091 Cycle 2

G = 1 /2 (11.091 + 110/11.091) = 10.5044 Cycle 3

G = 1 / 2 (10.5044 + 110/10.5044) = 10.488 Cycle 4

Example 6.

5 REMARK EXAMPLE 7, SQUARE ROOTS BY NEWTON
10 PRINT "WHAT VALUE*';
15 INPUT X
20 LET G = X
25 LET X = .5 * (G + X/G)
30 PRINT X

35 IF ABS (G/X - 1)>.0001 THEN 20
40 PRINT "THE SQUARE ROOT IS "; X
45 END

Example 7.

subsequent values of 55.5,
28.741, 16.2841, 11.5196,
10.5343, 10.4882, and 10.4881
as the final result. Adding some
analytical steps to get a better
first guess would make it con-
verge even faster.

I have tried to show you some
of the uses of loops, some of
the dangers and some of the

various styles. Once you
understand the idea, they are
easy to design. Your programs
will often be physically smaller
with loops than without, and
the principles can be applied in
any language. Try writing your
own programs incorporating
what you've learned here. I
think you'll enjoy it.B

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115

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•LEXAN"' GENERAL ELECTRIC

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Kilobaud Classified advertisements are intended for use by persons desiring to
buy, sell or trade used computer equipment or software. No commercial ads are ac-
cepted.

Two sizes of ads are available. The $5 box allows up to 5 lines of about 37
characters per line, including spaces and punctuation. The $10 box allows up to 10
lines. Minimize use of capital letters to save space. No special layouts allowed Pay-
ment ts required in advance with ad copy. We cannot bill or accept credit

Advertising text and payment must reach us 60 days in advance of publication
(i.e., copy for March issue, mailed in February, must be here by Jan. 1). The publisher
reserves the right to refuse questionable or not applicable advertisements Mail
copy w.th payment to: Kilobaud Classified, Kilobaud, Peterborough NH 03458. Do
not include any other material with your ad as it may be delayed.

TRS-80 Level I 4K— 5 pop. games. Orig.—
graphics & score— cassette, $7. C. Zalneru-
nas, 3034 W. Columbus Ave., Chicago IL
60652.

TRS-80 OWNERS!! Original software in-
cluding business system for Amway Dis-
tributors. Level I & II versions available. All
will run in 4K. Also have moving signboard
machine-language program. Write for info.
Allan E. Sitter, 8 Driftwood Circle, Groton
CT 06340.

TRS-80 Monthly Newsletter. For informa-
tion write to: Howard Y. Gosman, Box 149,
New City NY 10956.

•Books of computer games in BASIC.
ENIGMAS- 1 ($8): Gone Fishing, Concen-
tration, Starship, Craps, Slot-Machine,
Sherlock Holmes, Tank Attack.
ENIGMAS-2 ($8): Number Guess, Mortar
Battle, In-Between, Shell Game, Safari,
Starship-2, Dice Roll, Puzzle. 'Catalog and
test program Frog Race, Si. Available in
Standard BASIC, SWTP 8K BASIC or
Radio Shack TRS-80 BASIC. Please specify.
B. Erickson, PO Box 11099, Chicago IL
60611.

CIRCLE CHESS instruction book by
Alphonso, used in Circle Chess software
development, $5. Stanonis, Box 63, Des
Plaines IL 60017.

TRS-80 Level II, 16K. Star Trek game that
runs in Level II, $5.95. Other games SASE.
J. Joyce, 5925 Rockhill Rd., Kansas City
MO 641 10.

TRS-80, 16K memory kits. New (100«7o
tested), $175. Larry C. Stanley, Rt. 5, Box
131 B, CirclevilleOH43113.(614)474-1741.

Imsai 8080 mainframe with front panel, Z-80
CPU, 8080 CPU, Merlin video monitor,
TDL system monitor, Quantronics memory,
George Risk keyboard, software. $1635 up
and running. Virginia (804) 320-4439, eve-
nings.

TRS-80 Single Step, edit, breakpoints, full
display. J.5K, 18 commands, easy add-on.
Lev I or II, hi or lo mem. SASE for specs or
$14 for tape and Z-80 list to Sam Solomon,
6317 Eliot, Long Beach CA 90803.

TRS-80 LIFE, Level I, 4K. Patterns on 114
x 44 grid; up to 999 generations; popula-
tions to 680 on 4K, 3752 on 16K; $6. Send
SASE for details. D. MacAdam, 52 School
St., Chatham MA 02633.

We had replacement panels made for our
Altair 8800s. They're blue against a white
background and really look nice! We'll sell
the extras for $19 each. D.L. Tibbetts, 520
Schoolhouse Ln., Willow Grove PA 19090.

TRS-80 I or II: Data base manager, $20. In-
ventory, $20. Stock & bank acct., $15. Lunar,
gunner, slot, crap, $13. Poi Pow, % Dothan
St., Arlington MA 02174.

OTHELLO— The classic board game! Runs
in 4K on any 8080/ Z-80 micro, with VDM,
etc. Plays a good game against one player, or
referees for two. Now in Cuts, Tarbell and
Paper Tape. Comes with a 20-page manual
and tape for $12 postpaid from Dave Bell,
609 Craig, Campbell CA 95008.

North Star BASIC S/W. Universal File Or-
ganizer. Design custom file on line. Edit/
add/ modify/delete records. Search any/all
fields. BASIC, 24K mem.— $25. R. L. Marx,
1077 Ticonderoga Dr., Sunnyvale CA 94087.

TRS-80 (Level II) or North Star education
programs. "Spelling Bee" drills spelling
grades 2-8. Math drills too. Send $5 and disk
or cassette. Swap programs? F. Derfler, 1440
Aiea Hts. Dr., #25, Aiea HI 96701.

TRS-80 Programs: Star fleet Command— 2
player war game, 11 ships each, 16K; $10.
Star Trek— fast but not easy, 4K(L 1)-5K(L
2); $5. Specify Level 1 or 2. G. W. Scheil,
#1 18-1638 Bushman Drive, Kansas City MO
64110.

PET owners— need more than's in the man-
ual? PETABLE is an intro. to PET BASIC,
graphics, etc. Includes programs, exercises
and more. Send $4.95 to R. Mansfield, PO
Box 461, Philipsburg PA 16866.

PET owners— join our club and get "Pro-
gram," a monthly cassette. Articles, info.,
games, programs! Just load and go! $27 per
year. R. Mansfield, PO Box 461, Philipsburg
PA 16866.

SWTP two 4K memory boards, sockets, $90
ea. Blank MP-A processor board, $10. E.
Skarjune, Detroit, (313) 386-6566.

For Sale: Imsai PCS-80/35 with TV moni-
tor, dual mini-diskettes, 32K, Imdos
(CP/M), BASIC-C, keyboard, VIO-C and
spare port for printer. Almost new; will sell
for $3000. T. Aho, 3965 Munkers SE, Salem
OR 97301. (503) 581-9566.

APPLE II SSTV software. Display slow-
scan TV pictures in hi-res graphics. Software
demodulated— just connect rcvr audio to
Apple— no hardware needed! Req. 16K. On
cassette with test pictures, $18. Listing only,
$12. C. H. Galfo, 602 Orange St., Char-
lottesville VA 22901 .

APPLE II ham radio software — send & rev
in Morse, Baudot or ASCII. Variable size
text buffer; 3-field screen display; stored
messages & more features. Uses on-board
(game) I/O. Req. 8K. On cassette, $18. C.
H. Galfo, 602 Orange St., Charlottesville
V A 22901.

Free Programs— TRS-80 Swap Club form-
ing .. . Send me your favorite programs (on
cassette). No Blackjack, Backgammon or
programs from TRS-80 Manual please ... I
will send you a few of my favorites (on
cassettes). Please enclose $1 .00 to help cover
my postage. Steve Coleman, 17 N. Main St.,
K-l, Washington Crossing PA 18977.

Must Sell!! SOL 20— 24K RAM— Panasonic
monitor, cassette— North Star controller
with Shugart SA400 disk drive— music inter-
face board— 15K extended cassette BASIC
— 12K disk BASIC— game pack 1— every-
thing works— less than 6 months old— $3400
value for $2995 J. Andrews, 6303 Kury,
Houston TX 77008. (713) 869-3985 (eve.)

S- 100 system for sale. 8080 with 48K of static
RAM, 108-key keyboard, video display,
Selectric, paper tape reader, Tarbell cassette
system, EPROM programmer and eraser
and over 100 programs. $3600. Jim Baum-
gardt, 6821 San Alto, Buena Park Ca 90620.
(714) 826-7056.

For Sale: COSMAC Elf II power supply,
user manual, P. E. reprints & Elf Newslet-
ters. $70. T. Hazelett, 2107 Capitol Dr.,
Parkersburg WV 26101.

Tutor programs in BASIC teach computer-
developed winning Blackjack system. For
details write: Roy Schoeller, PO Box 22472,
San Diego C A 92122.

For Sale: Apple II software-cassette:
Author-Title Index program for books,
records, tapes. Super-fast machine-lang.
sort. 16K Blackjack, graphic, paddle input,
sound, full L. V. rules, auto-play by com-
puter: $10 each incl. doc. Both for $15.
George W. Lee, 18803 S. Christina Ave.,
CerritosCA90701.

GTE Diablo terminal; letter quality
printer/keyboard; RS232 interface. Gross-
man, 410 Albany Post Road, Croton NY
10520.

ADM-3 Lowercase parts kit with complete
instructions, $39.00. Nancy G., 57 Manor
Drive, Hudson OH 44236.

TRS-80 Software on tape. Games and more
SASE for more info. Liberty Ridge, R.3,
Box 44B, Rockport IN 47635.

RS-232 interface for Diablo printer w/CDC
I/O as adv. in May KB. $250. H. Stone, 64
Morgan, Amherst MA 01002.

Original PET Software! A variety of action
games with graphics and sound effects, use-
ful math routines, interfaces (Teletype,
parallel printers and telephone) and a pro-
gram for creating, saving and playing back
music. Send for a free catalog today. Peter
Ruetz, 368 Albion Ave., Woodside CA
94062.

Wanted. North Star BASIC Compiler.
Roger T. Scaggs, 2353 Claridge Circle,
Piano TX 75075. (214) 596-1212.

Swap Altair 8800B w/front panel, 56K
RAM, full-size floppy disk, 4.1 disk BASIC,
DOS, 2SIO, Heath H9, ASR-33 Teletype (1
year old) complete & operational for best
small plane offered. Send picture & offer to:
SWAP, 571 Bayonne Ct., SE, Salem OR
97301.

Heath H8; 16K boards factory checked. H9
terminal— 2 cassette machines. Program-
ming course— collection of computer books
—will ship: $1500 firm. P. Morgan, PO Box
638, Gaffney, SC 29340. Bus. hrs. (803)
489-7272.

Heath Hll assembled, tested w/4K. Pre-
paid, insured in C.U.S. by UPS. $1425 certi-
fied check only. J. H. Cowden, 3903 Sierra
Drive, Austin TX 78731.

Hungry PET? Casino Pac I contains Black-
jack with full graphics including face cards,
Craps and Slot Machine with spinning reels,
falling coins & more. For 8K. Send $10 for
cassette. Add $3 for plans for simple audio
interface & Slot Machine with sound effects.
J. Petrey, 3208 Navajo Way, Las Vegas NV
89108.

Peripheral Vision S-100 floppy controller,
Innovex full-size drive, power supply,
FDOS; $600. G. Weber, 1801 N. Line St.,
Lansdale PA 19446. (215) 362-9031.

Software: Apple II programs from Astro-
Graphics Software. 16-color Life game,
$6.50; Hires drawing program (draws &
saves any shape), 16 & 20K, $12; astrology
calculation program (Ephemeris needed),
$10; Number converter bases 2-16, $5;
graphics package, $3; robots game, $7.50.
Send for current list to: AstroGraphics Soft-
ware, 140 Willow Ave #2, Fairfax CA 94930.

If you've been following our "best article of the month" con-
test, you know that we'll be putting a year's worth of winners on
a ballot, and the winner in that balloting will win $500.

The contest started with the October 1977 issue; the winner
for August 1978 has been chosen already, which means we
have one month to go. September's winner and the ballot will
appear in the next issue.

So— dust off your back issues and get ready to make one of
our authors $500 richer.

By the way, the winner for August is Donald L. Fitchhorn,
author of "DOCUFORM," by a landslide.

The winner in our drawing of all votes submitted is John S.
Turner of Monroe Ml. He wins a book from the KB Book Nook.

Congratulations, Don and John, and thanks to all our readers
who have responded so enthusiastically with their votes.

118

COMPUTER CANOPY

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Dealer Inquiries Invited

Same day shipment. First line parts only. Factory
tested Guaranteed money back. Quality IC's and
other components at factory prices.

INTEGRATED CIRCUITS

P.O. Box 4430M Santa Clara, CA 95054
For will call only: (^8) 988-1640

74MTTL

7400N I

7402N 1

7404N I 1

7409N ?

7410N 1

7414N 6

7420N 1

7422N I 3

7430* Z

7442N S

7445N 6

7447N 6

7448N 6

7450N 1

7474N 2

7475N 4

748SN 8

7489N 2

7490N 4

7492N 4

7493N 4

7495N 8

74100* 9

74107N 2

74121N 3

74123N 5

74125N 3

74 MSN 6

741SON 9

74151N 6

74154N I

74157N 6

74161N 8

74I62N 8

74I63N 8

74174N 9

74175N 9

74190N I I

74192N 8

74193N 6

74221N 1 S

74298N 1 e

74365N i

74366N C

74367N f

741 $80 TTL

74LSOON ;

74LS02N !

74LS04N ;

74LS05N !

74LS08N ;

74LS10N ;

74LS13N '

74LSUN !

74LS20N i

741S22N i

74LS28N

74LS30H

74LS33N

74LS38N

74LS74N

74LS75N

74LS90N

74LS93N

74LS95N 1

74LS107N

74LS112N

74LS113N

74LS132N

74LSI36N

74LS151N

74LS155N

74LS157N

74LS162N

74LS163N

74LS174N

74LS190N

74LS221N

74LS258N

74LS367N

LINEAR

CA304S

CA3046

CA308I

CA3082

CA3089

LM301AN AH

IM305H

LM307N

IM308N

LM309H

LM309K

LM311M N

LM317TK

LM3I8

LM320K-5

LM323K 5 I

LM320K 12

LM320K-15

LM320T 5

LM320T8

LM320T 12

LM320T-15

LM324N

LM339N

LM340K 5

LM340K-8

LM340K 12

LM340K 15

IM340K-24

IM340T5

IM340T 8

LM340M2

LM340T IS

LM340T 18

LM340T 24

LM343H

LM370

LM377

LM379

LM380N

IM381

LM382

LM703H

LM709H

LM723HN

LM733N

LM741CH

LM741N

LM747H/N

LM748N

LM1303N

LM1304

LM1305

LM1307

LM1310

LMW58

LM1800

LM1812

LM1889

LM2111

LM2902

LM3900N

LM3905

LM3909N

MC 1458V

NE540L

NE550N

NE555V

NE556A

NE565A

NE566V

NE567V

NE5708

NE571B

78105

78108

79105

78M05

75108

75491 CN

75492CN

75494CN

CMOS

CD34001

CD4000

C04001

C04002

CD4006

C04007

C04008

CD4009

C04010

CD4011

CD4012

C04013

CD4014

CD4015

CD4016

CD401 7

C04018

C04019

C04020

C04021

C04022

C04023

C04024

C04025

CD4026

CD4027

C04028

CD4029

C04030

C04035

CD4040

C04042

C04043

C04044

C04046

CD4049

CD4050

C04051

CD4060

C04066

C04068

CD4069

CD4070

CD4071

CD4072

C04073

CD4075

AMD CONVERTER C04076

8038

8700CJ

8701 CN

8750CJ

LD130

9400CJVF

ICI7103
W.7107

CD4078 40
CD4081 21
CD4082 21
C04116 47
CD4490 5 50
CD4507 1 00
C04508 4 25
C04510 1 02

C04511 94

C04515 2 52

CD4516 1 10

C04518 1 02

CD4520 1 02

C04527 1 51

C04528 79

C04553 5 75

CD4566 2 25

CD4583 4 50

C04585 1 10

CD40192 3 00

74COO 28

74C04 33

74C10 28

74C14 2 10

74C20 28

74C30 28

74C48 1 95

74C74 75

74C76 1 40

74C90 1 15

74C93 1 40

74C154 3 00

74C160 1 44

74C175 ' 35

74C192 1 «5

74C221 2 00

74C905 3 00

74C906 75

74C914 1 95

74C922 5 M

74C923 5 50

74C925 6 95

74C926 6 95

74C927 6 95
INTERFACE

8095 65

8096 65

8097 65

8098 65
8T09 1 25
8T10 4 50
8T13 3 00
8T20 5 50
8T23 3 10
8T24 3 50
8T25 3 20
8T26 1 69
8T28 2 75
8T97 1 69
8T98 1 69
M0S/MEM0RY
RAM

21011 3 95

2102 1 1 28
2102AM 1 60

21F02 1 85
2104A-4 4 95

2107B 4 95

21111 4 95

2112 2 3 95

7114

MM116

2513B

21102 1

MM5262

MM5280

MM5320

MM5330

PD411D-3

PD4HD4

P5101L

4200A

82S25

91L02A

HD0165-5

MM571O0

GIAV38500 -1

MCM6571A

9368

CLOCKS

MM5309

MM5311

MM5312

MM5313

MM5314

MM5315

MM5316

MM5318

MM5369

MM5841

MM5865

CT7001

CT7002

CT7010

CT7015

MM5375AA/N

MM5375AB/N

7205

7207

7206

7209

OS0026CN

DS0056CN

MM53104

2322 Walsh Ave.

SIC/

ELECTRONICS

8251
8253
8255

CDP1802C0
CDP1802D
CDP1861
6820
6850
6502

UART FIFO
AY5I013
AV5 1014
3341
PROM
1702A
N62S23
N82S123
N82S126
NS2S129
N82S131
N82S136
N82S137
2708
DM8577
8223
2716T1

CONNECTORS
44 pin tdgt
100 pin edge

9 25
10 00

925
1995
25 00
12 95

995
12 95

'8 W

IC SOCKETS
Soltfer Tin Ln Prattle

3 level awl »>W POM
14 pm 25 *6 pin

?tMI 14 p^ w* <fj

MICROPROCESSOR

6800 19!

8080A with dill 8 <

780 29!

8212 2!

8214 61

8216

8224

8228 5 :

100 pin
CRYSTALS

1 MHi

2 MHz

4 MHz

5 MHz
10 MHz
18 MHz
?0MHz
32 MHz
32768 Hz

1 6432 MHz
3 5795 MHz

2 0100 MHz

2 097152 MHz

2 4576 MHz

3 2768 MHz
5 0688 MHz
5 185 MHz

5 7143 MHz

6 5536 MHz
14 31818 MHz
18 432 MHz
22 1184 MHz

200

450

WW 5 25

CLOCK MODULES Complete alarm clocks
ready to hook up mm transformer and
switches Very compact wilti 50" and
84dmits

MA1002A CnE 50 IN

lim TniMinMi 2 25

MA1010A C Of E S4 11 M

102P2 Traealermer 2 25

Special Maeianaer and Mi i«**ee

MfR ^P4W^Nw*af4f^Plal Wrmf^Kf^fJ a^m

WIW ear aMNWa I
•reeaflaa* Heato* ISM

resistors a am 5%

10 pei type 03 1000 pet type 012
25 pat type 025 350 piece pack
100 par type 015 5 pet type 6 75

KEYI0AR0S

Hei keyboard Si 95 Fully encoded *

PC board parts and mUructs S24 95

53 key ASCII keyboard kit 55 00

Futy assembled 65 00 Endoaure 14 95

LEOS

Red T018 - 15

Green Orange YHIo* T018
Jumbo Red

Green Orange Ye*o« Jumbo 25

ClleUta LEO MaaaNng Cllae 8$1 25
(specify red ambar green yeeoo clear)

CONTINENTAL SPECIALTIES M Mack
Complete line of breadboard test equip
MA* 100HI|I1 Free. Of $178*5

OK WIRE WRAP TOOLS m Had
Ponakle MeHlmeter SIS M

DIGITAL THERMOMETER S4S M

Bait oper General purpose or medical
32 230"F Disposable probe cover • 2
accuracy Comp assy in compact case
COMPUTER 80AR0 KITS
8K RAM Board Kit $134 95

4ii f PROM kit 114 95

10 Board Kit 44 50

Extender Board <• connector 12 50

Video imartace board kit 125 00

16k EPSOM board U . o PROMS 74 50
16K Static RAM board kit 395 00

Nartk Star FNaaay Otak KN S665 00
Additional Orive Kit 415 00

SPECIAL PROOUCTS
MM5865 Stopwatch Timer 9 00
PC board 7 50

Sattckei Mom Pushbutlon 27
3 pos skde 25

EM4MMV HD0165 5 6 95

3 DlfK Universal
Ceerrter leer* KH
Operates 5-18 Volt DC to 5 MHz
typ 125 LEO display II M

Voice actuated switch 50

Paratraalcs 100A Loflc
Aaalytar KM

Model 10 Trigger

Eipander Kit
Model 150 Bus

Grabber kit

6V300 ma

12 Vort 300 ma transtormer

12 6V CT 600 ma

12V 250 ma wall plug

12V CT 250 ma wall plug

24V CT 400 ma

10V 1 2 amp wan plug

18V 6 amp

DISPLAY LEOS

MAN1

MAN3

MAN 72 74

DL704

DL707'DL707R

DL727 728

SIM 00

$229 00
$369 00

CA/CA

CAjCC

CA/CC

COCA

CCCA

CC/CA

270 2 90

125 39

300 1 00

300 1 25

300 1 00

500 1 90

DL747 750

01750

FN0359

FND5O0/507

FN0503510

FND800.807 CC CA 800 2 20

3 digit Bubble 60

4 digit bubble SO
DG8 Fluorescent 1 75
DG10 Fluorescent 1 75

5 digit 14 pin display 1 00
NSN69 9 digit display 60
7520 Ciairn photocell 39
TIL311 Hen 9 50
IC Test Clips

1 II

Red 55 47

Black 55

Kayar 8043

comp w spec sock

Sinclair 3V 2 Digit Multimeter

Batt /AC oper. "ImVand 1NA resolution
Resistance to 20 meg. 1 % accuracy. Small,
portable, completely assem. incase 1 yr
guarantee Best value ever!

Not a Cheap Clock Kit $14.95

Includes everything except case. 2-PC
boards 6-50" LED Displays. 5314 clock
chip, transformer, all components and full
instrucs Green and orange displays also
avail Same kit w .80 displays. $21.95

Digital Temperature Meter Kit

Indoor and outdoor. Switches back and
forth. Beautiful. 50" LED readouts. Noth-
ing like it available Needs no additional
parts for complete, full operation Will
measure -100 to • 200 F, tenths of a de-
gree. air or liquid Very accurate $39.95
Beautiful hardwood case w/bezel $11.75

NiCad Batt. Fixer/Charger Kit

Opens shorted cells that won't hold a
charge and then charges them up, all in
one kit w/full parts & instruc. $7.25

RCA Cosmac VIP Kit 275.00

Video computer with ga mes and graphics

78 IC Update Master Manual

1978 IC Update Master Manual $30.00
Complete IC data selector 2175 pg. Mas-
ter reference guide. Over 42,000 cross
references. Free update service through
1978 Domestic postage $3 50. Foreign
$6 00 Final 1977 Master closeout $15.00

New Cosmac Super "ELF"

RCA CMOS expandable to 64K micro-
computer w/HEX keypad input and video
output for graphics Just turn on and
start loading your program using the resi-
dent monitor on ROM. Pushbutton selec-
tion of all four CPU modes. LED indicators
of current CPU mode and four CPU states
Single step op. for program debug. Built
in pwr. supply. 256 Bytes of RAM, audio
amp. & spkr 100 pg. detailed assy man.
incl. new exten. software section. PC
board solder masked & all parts fu»y
socketed Comp. Kit $106.95 High ad-
dress display option 8.95; Low address
display option 9.95; Custom hardwood
cab.; drilled front panel 19.75; Nicad
Battery Backup Kit w/all parts 4.95; Fully
wired & tested in cabinet 151.70. Quest-
data 1802 software club. 10-12 pg
monthly publication 12.00 per yr

4K Elf Expansion Board Kit
with Cassette l/F $79.95

Available on board options: 1K super ROM
monitor $19.95 Parallel I/O port $7.95
RS232 l/F $3.50 TTY 20 ma l/F $1.95
S-100 Memory l/F $4.50

Tiny Basic for ANY 1802 System

Cassette $10.00. On ROM Monitor $38.00.
Super Elf owners, 30% off Object code
listing or paper tape with manual $5.50.

Original ELF Kit Board $14.95

60 Hz Crystal Time Base

Kit $4.40 Converts digital clocks
from AC line frequency to crystal time
base. Outstanding accuracy Kit includes:
PC board, MM5369, crystal, resistors,
capacitors and trimmer.

Clock Calendar Kit $23.95

CT7015 direct drive chip displays date
and time on .6" LEDS with AM-PM indi-
cator Alarm/doze feature includes buz-
zer Complete with all parts, power supply
and instructions, less case

2.5 MHz Frequency Counter

Kit Complete kit less case $37.50

30 MHz Frequency Counter

Kit Complete kit less case $47.75
Prescaler Kit to 350 MHz $19.95

PROM Eraser tAQ Q ,

Ultraviolet, assembled » , »»• ,,^

Video Modulator Kit $8.95

Convert your TV set into a high quality
monitor without affecting normal usage
Complete kit with full instructions

Stopwatch Kit $26.95

Full six digit battery operated 2-5 volts.
3 2768 MHz crystal accuracy Times to
59 min , 59 sec , 99 1/100 sec. Times std. ,
split and Taylor 7205 chip, all compo-
nents minus case Full instruc .

Auto Clock Kit $15.95

DC clock with 4-50" displays. Uses
National MA- 101 2 module with alarm
option Includes light dimmer, crystal
timebase PC boards. Fully regulated,
comp instructs Add $3.95 for beautiful
dark gray case Best value anywhere

TERMS: $5.00 min. order U.S. Funds. Calif residents add 6% tax
BankAmericard and Master Charge accepted.
Shipping charges will be added on charge cards.

FREE: Send for your copy of our NEW 1978
QUEST CATALOG. Include 28* stamp.

119

"Hey, Bill! You want to give me a hand?
We've got another necktie caught in the disk
drive."

WKill Oko sf oU

GlGlDEIalFc

UBHIllBIBlBIBlBlBlffll

electronic calculators

LIST

$299.95

124.9S

59.95

49.95

59.9S

99.95

LIST

5750.00

450.00

275.00

175.00

325.00

100.00

90.00

495.00

120.00

75.00

HAM MET

5259.95

112.45
53.95
44.95
53.99
92.95

TEXAS INSTRUMENTS ELECTRONIC CALCULATORS

T.I. -59, 990 STEP PROGRAMMABLE SCIENTIFIC
T.I.-59, 490 9TEP PROGRAMMABLE SCIENTIFIC
T.I.-57, 150 STEP PROGRAMMABLE SCIENTIFIC
T.I.55, 32 STEP PROGRAMMABLE SCIENTIFIC
T.I. PROGRAMMER, CONVERTS DECIMAL OCT AL HEX
T.I. MBA, SUPER PROGRAMMED FINANCIAL

HEWLETT-PACKARD ELECTRONIC CALCULATORS

5975.00

405.00

247.50

157.50

292.50

90.00

72.00

54.00

445.50

109.00

07.50

H.P.-97, 224 STEP PROG SCIENTIFIC PRINT/VISUAL

H.P.-57, 224 STEP PROG SCIENTIFIC

H.P.-19C, 99 9TEP PROG SCIENTIFIC PRINT/VISUAL

H.P.29C. 99 STEP PROG SCIENTIFIC

HP 1 BASIC NAND NELD PRINTER VISUAL

HP 91, PREPROGRAMMED SCIENTIFIC PRINT/VISUAL

H.P.-33E, 49 9TEP PROG SCIENTIFIC

H.P.32E, PREPROGRAMMED SCIENTIFIC WITH STAT

H.P.-31 E, PREPROGRAMMED SCIENTIFIC

H.P.92. PREPROGRAMMED FINANCIAL PRINT VISUAL

H.P.-39E 9TEP PROGRAMMABLE 9UPER FINANCIAL

H.P.-37E, PREPROGRAMMED FINANCIAL

rlScr?SJe H ^?A- L i;ytftI?5 (S) INDICAT ED BELOW, COMPLETE WITH INCLUDED AC-
?5???r- R .'!?: INSTRUCTIONS, AND MANUFACTURERS WARRANTY. I UNDERSTAND

rn^7o F c l T A c M or?L?S )M £kl TELY SATISFIED, I MAY RETURN IT WITHIN 10 DAYS FOR A
COMPLETE REFUND (LESS SHIPPING).

MODEL(S).

.QUANTITY

AMOUNT ENCLOSED $

WE HONOR

VISA

MASTERCHARGE

MONEY ORDERS

COD

S^n™°^ P 5- S J A S E AND HANDLING. PLEASE ALLOW 10 DAYS FROM DATE OF
RECEIPT OF ORDER FOR DELIVERY. TEXAS RESIDENTS ADD 5% SALES TAX.

CARD NUMBER

FULL NAME

STREET

EXPIRATION DATE

CALL

CITY

STATE.

ZIP

MORE LITERATURE MODEL(S)

DEALER INQUIRIES INVITED'

H26

Hartwdfs
Offfce\VbridJnc.

MAIL TO: 6810 LARKWOOD

HOUSTON, TEX 77074

ATTN: STEVE, WA50EN

PHONE: A.C. (713) 777-2673

WE «TOCK ALL HtWHTT^ACK AWP CALCULATOH tomutt AND ACCESSORIES la!

PET 2001 • PET 2001 • PET 2001 • PET 2001 • PET 2001 • PET 2001 • PET 2001 y,

8K KIM EXPANSION SPECIAL

TWO 4K RAM KITS

KIM INTERFACE KIT

COMPLETE 8 SLOT MOTHERBOARD SET

WITH CABLE

$ 219.00

$245.00 If purchased separately

YOUR TICKET TO LOW COST SYSTEM EXPANSION

SEMICONDUCTOR PRODUCTS W13

25 SOUTH 300 EAST SUITE 215 SALT LAKE CITY, UTAH 84111 714/752 1374

I-
IAJ

a.
§

PET™

DOCUMENTATION

NOW!

TIS

WORKBOOKS FOR THE COMMODORE PET 2001
Getting Started with Your PET WB-1 $4.00

Covers the fundamentals of PET BASIC: calculator
and program mode, data input and output, data
representation, program storage on the cassette.

PET String and Array Handling WB-2 $3.95

Covers string and substring search, concatenation,
replacement and manipulation.

PET Graphic* W B-3 $4 95

Covers use of cursor control and special graphics
symbols to draw plots, histograms, and sketches.
PET Cassette I/O WB-4 $4 .95

Covers OPEN, CLOSE, string and numeric data files.
Miscellaneous PET Features WB-5 $3.95

Covers the clock, random number generator, upper
and lowercase alphabetic characters, saving memory
space, etc.

Add $1.50 for shipping and handling.

TIS
T41 P.O. Box 921

Los Alamos, NM 87S44

Money back guarantee

IV)

-4

T>
m
H
ro

•

H
ro

•

H
ro

■D

Pet is a trade mark of Commodore Business Machines *>

• PET 2001 • PET 2001 • PET 2001 • PET 2001 • PET 2001 • PET 2001 • PET 2001

120

APPLE-II USERS

Good news! Now you can save money buying 16K
of memory for $160.00 or 32K of memory for
$300.00!!! Unbelievable!!! We have Motorola
Prime Dynamic RAMs which are 250nS, rather
than the usual 450nS. For conversion follow in-
structions in your Apple II-Manual. We also in-
clude 3 programmable DIP Shunts with each
order for your convenience.

786-A 16K Dynamic RAMS $1 19.95
786- A 2 32K Dynamic RAM $300.00

DELTRONIKS D28
P. O. Box 29363
Atlanta, Ga. 30359

(404) 458-4690

PET SOFTWARE

PARENTS AND TEACHURS l«t your PET do th«
ln« true ting on any subject.

Wl»«» can use the PET(no pro*ra»aln* Icnowledate
necessary), to Instruct the children. You can
study these programs while learning data files.

COMPUTER TUTOR

CASSETTE CONTAINS i

(1) All -Purpose TUTOR program

(2) Auto-Prompt lng Entry Data program

(3) sample quiz on Datn Tape
Documanatlon, Worksheet, Listing

Hanu selection of up to four subject display
pages and 26 multiple choice questions. All
In upper and lower case. Requires 8K PET

COMPUTER TUTOR

2 programs A data

file on cassettes postpaid

COMPUTER TUTOR * T.l.S.

PET CASSETTE workbook t 13.95

COMPUTER TUTOR

317 Elm St.
Helena, Ark.

* ^ cSpute* ssrff .^as^-r JS&m +

Now Featuring:

APPLE II PROGRAM CASSETTES

Intelligent Game Series #1 offers many hours of chal-
lenging competition against any APPLE II. Available in
bargain packages:

t) BATTLESHIPV3DTICTACTOE

2) CONCENTRATION* /HANGMAN

3) CASINO ROY ALE (1 -Arm Bandit,
BackJAck, Crap Game & Rou-
lette) • Denotes APPLESOFT II Required

All programs feature APPLE II low and high resolu-
tion color graphics with convenient, personal in-
teraction. Each package costs $12 or $8 pet program,
instructions included, to be paid in advance. In-
dividual listings can be obtained for an additional
charge of $3.00 per program. Send for free, full
descriptions on all available software. Write to:
-U7

U ASKED 4 IT COMPUTER SOFTWARE
P.O. BOX 13331, BALTIMORE MD 21203

gysn $0U1 B"UKAST9I

BTHS

BASIC FLOPPY DISK SYSTEM

• RANDOM ACCESS FILES

• ANY NUMBER OF FILES MAY BE OPEN (IN USE) AT ONE TIME

• THE NUMBER OF FILES AND SIZE OF FILES IS LIMITED
ONLY BY THE SIZE OF THE DISK

• MERGING FILES REQUIRES NO EXTRA DISK SPACE

• NO WAITING FOR THE DISK TO RE-PACK

• LONGER DISK LIFE-MORE EVEN DISK WEAR

We delivered our first mini-floppy disk system a year and a half ago — 6 months
ahead of any other 6800 based mini system. Since that time, it has earned the reputa-
tion of being the most reliable mini-disk system available.

This system comes completely assembled with a disk controller that is plug com-
patible with the SWTPC 6800. In fact all our products use the 6800 standard SS-50
(Smoke Signal 50) bus used by SWTPC. The cabinet and power supply are capable of
handling up to 3 Shugart Mini-Floppy Drives. One drive is included in the price of the
BFD-68 and others may be added easily at any time. Or you may save money by order-
ing the dual-drive BFD-68-2 or triple drive BFD-68-3 (pictured). Price: BFD-68
$795, BFD-68-2 $1 139, BFD-68-3 $1479, SA-400 Drive $355.

A bootstrap PROM is included on the controller board to initiate the Disk Opera-
ting System. Thus, you can be up and running from a cold start in just a few seconds.

SUPER SOFTWARE

The BFD-68 includes our new expanded disk operating system and disk file hand-
ling BASIC interpreter. In addition, the BFD-68 is supported by the most complete
microcomputer software available today. This includes an excellent editor and text
processor, several assemblers and a BASIC compiler.

Send for FREE NEW Computer Products Catalog

SMOKE SHffiAi BBOAMASTIIG

6304 Yucca/Hollywood, CA 90028/(213) 462-5652

S46

121

THIS ONE WILL FIT!

iBieot

STACKBD®

New STACKBD® & Z-Bus® concepts with powerful, fast Z80 CPU
with RT Clock provide flexibility, compactness, reliability. Inexpensive
32,000 byte dynamic RAM Boards allow over 2 million bytes on line.
PIO boards provide 64 I/O lines each. ROM boards; Interfaces for CRT,
Cassette, Plasma Display, A/D, RS-232C, TTY, Keyboard, Printer.
Assembled system prices, $299.00 up.

D38

ECONOMICAL CUSTOM ELECTRONIC
HARDWARE Lf SOFTWARE

Write for details:

DNA 30147 Via Borica
Palos Verdes, CA 90274
(213)541-2220

SOFTWARE!

canned
software

YES! QUALITY SOFTWARE FOR THE TRS-SO IS
NOW WRITTEN & AVAILARLE. RCC IS PLEASED
TO BE ABLE TO PRESENT SOME VERY FINE
SOFTWARE NOW WITH EVEN MORE AVAIL-
ABLE IN THE VERY NEAR FUTURE. ALSO WE
DEVELOP CUSTOM DESIGNED SOFTWARE FOR
YOUR EVERY NEED. WRITE US FOR A FREE
PRICE QUOTE.

WHEN YOU THINK SOFTWARE THINK BCC

EXPENSE REPORTING SYSTEM — $22 95 Level

Requires 16K of RAM. Keeps track of up to 50 Expense Categories for a ful
year. Gives monthly, quarterly, and annual totals of expenses. For the small
business or home use.

BACKGAMMON — $19.95 Levels I & II

Requires 16K of RAM. PLAY AGAINST THE COMPUTER and lose. The com-
puter plays a pretty good game!

SPACE TREK-80— $9.95 Levels I & II

Requires 16K of RAM. Play a strange game of blowing-up stars to find star-
bases. Watch out for those antimatter mines. Tune-in on your AM radio for
strange sound effects.

□ ASTRONOMY SIGHT REDUCTION— $24 95 Levels I & II

Requires 8K of RAM. For Astronomers. Convert Right Ascension and Declination of
celestial objects to Azimuth (compass dir.) & altitude (degrees). Creates a 24 hour
table in siderial and standard times.

ORDER NOW! All programs come on quality cassettes. Programs are available
on diskette for an additional charge of $7.00 per order. NYS residents add 7%.

(All items must be

Check boxes of items being ordered:

# of items ordered Total amount enclosed

prepaid.)

®@mml£ C@(ra§yOtfD(raD C@if[p>®iF®tiii®iR)

B35

11 friendly rd.
smithtown ny 11787

Dept. TRS - 80

ATTENTION COMMODORE PET* OWNERS

Run) S 100 MPA

M pi rATnAlllAA (MEMORY + PERIPHERALS ADAPTER)

(FORMERLY THE PETS 100)

ELECTRONICS

AN S-100 BUS ADAPTER FOR THE COMMODORE PET

• PLUGS INTO ANY S-100 BUS MAINFRAME

• CONNECTS TO PET VIA RIBBON CABLE (PROVIDED)

• FULL S-100 BUS EMULATION

• USE DMA DEVICES LIKE CROMEMCO DAZZLER™

• EXPAND THE PET'S MEMORY & I/O

• MEETS PROPOSED IEEE S-100 BUS SPECS

• EASY TO ASSEMBLE- SOLDER MASK, LEGEND & SOCKETS

• $199.95 KIT, $279.95 ASSM. & TESTED + 5.00 SHIPPING.

The S-100 MPA was the FIRST and is still the BEST S-100 Bus Adapter, on the market. This well thought out board actually meets
the proposed IEEE specifications tor the S-100 Bus which insures compatability tor the widest range ot S-100 Bus peripherals Now you
can easily expand your PET s memory and I/O capabilities

THE S-100 MPA CAN ALSO BE A STAND ALONE 6502 CPU BOARD FOR THE S-100 BUS

With the addition ot a 6502 chip and a tew other components, the S-100 MPA becomes a stand-alone CPU board for the S-100
Bus — the onty one to offer such complete compatability Just order the Stand-Alone Option Kit for an additional $49.95.

OTHER HUH ELECTRONICS ACCESSORIES FOR YOUR COMMODORE PET*

The BEEPER— Automatically beeps when cassette LOADS and SAVES are completed. Also can beep under
program control. Just $24.95 • 2.00 shipping. Fully assembled and tested.

The PETUNIA— Music Board that is actually an 8-bit DAC. Our software makes it play up to four notes at once.
Software included. External amp and speaker required. Just $29.95 • 2.00 shipping and
handling Fully assembled and tested.

The VIDEO— Allows use of a standard monitor or TV with the PET. Great for classroom or remote viewing.
BUFFER Designed so that M&R Enterpnses SUR R MOD II plugs nght on allowing use of Standard TVs.

Just $29.95 « 2.00 shipping and handling. With SUP R'MOD II for standard TV's— $59.95

2 00 shipping and handling Assembled and tested.
The COMBO— A Petunia and a Video Buffer all on one board. You save $10.00!! $49.95 I 2.00 shipping and

handling— with SUP'R MOD II— $79.95 • 2.00 shipping and handling.

ALL HUH ELECTRONICS PRODUCTS ARE AVAILABLE FROM STOCK FROM LEADING
COMPUTER STORES OR FACTORY DIRECT CALL OR WRITE FOR MORE
INFORMATION.

1429 MAPLE STREET
SAN MATEO, CA 94402
(415) 573-7359

ELECTRONICS H29

COMING SOON: TRS-80 to S-100 Bus Adapter'!'
See us at the 3rd. West Coast Computer Faire. LA
—Booth #31 1
DEALER INQUIRIES INVITED

•PET IS A TRADEMARK OF COMMOOORE BUSINESS MACHINES

progr^

DATA1-K RESIDENT

ASSEMBLER/EDITOR

FOR THE

MOS TECHNOLOGY 6502

The DATA1-K resident assembler/editor is the new,

efficient approach to the assembly of microcomputer programs.

All assembler editor functions are performed entirely

within memory. In most cases there is no need for a special

computer system! Program with the DATA IK on the

system which will ultimately make use of the obiect code. This

not only lowers the initial cost of a development system but greatly

decreases the amount of time spent on program debugging.

The DATA1-K assembles fast -over 600 lines per minute-and uses

the standard MOS Technology Assembler Language. The DATAt-K

features a truly general purpose line oriented text editor with error correction and

paged output capability. The DATA1-K is currently in use by: General Electric. Western

Electric, Eaton. Monitor Systems, the University of Cincinnati, and many others.

It is presently available on KIM-1 format paper tape or cassette and it includes one year
warranty and update.

Price: $250.00

Available from Johnson Computer, P.O. Box 523, Medina, OH 44256. Phone: (216) 725-4560.
Terms: Payment with order/add S2.00 shipping and handling/ add S10.00 for cassette version.
Delivery: stock to 30 days.

ALSO AVAILABLE IN CASSETTE

IOHNSON

iVl P. O.'BOX 523 MEDINA, OHIO 44558

122

A price
that's hard to beat.

Because of new technology and high-volume company
sales, Central Data Corporation has reduced the price of
its 16K RAM board by $40 and its 32K RAM board by $50.
Plus, we now offer full 48K and 64K RAM boards. Our 16K,
32K, and 48K boards are expandable to 64K in 16K incre-
ments.

• 16KRAM— $249 • 48K RAM— $599

• 32K RAM— $425 • 64K RAM— $775
• Memory Expansion Package ( 1 6K) — $ 1 85

As always, our boards come complete — fully assembled,
burned-in, and ready to use.

A product
that's better than ever.

We've also made improvements to our board's design at
no extra cost to you.

• Deselectable in 2K increments. Our deselect
feature enables you to switch off any 2K to avoid
overlap with your existing memory.

• Fully socketed memory. This feature enables you
to expand the memory board yourself.

• Plug selectable addressing. Mow you can re-
address without soldering.

m\i\

\ m m

::i:i :i: T

.am

Central Data Corporation's RAM Board

Standard Features

• Power-saving dynamic board with on-board invisible
refresh

• One-year guarantee on parts and labor

• S-100 and Z-80 compatible

For specifications and other information, or to place an
order, contact:

Central Data Corporation

P.O. Box 2484, Station A

Champaign, IL 61820

Ph.(217)359-8010

C91

CATCH THE S-100 BUS

North Star Horizon 1 Kit
North Star MDSA Kit

With Power Supply,

Cabinet and Three

Extra Diskettes
VeTbatirn diskettes (5 1 /a")
Solid State Music VB1B Kit
Imsai 8080 Kit

LIST
PRICE

1599 00
699 00

SPECIAL
CASH
PRICE

1339 00

589 95

790 50

659 95

450

380

149 95

124 95

699 00

569 95

Dynabyte250ns16K
Static Memory Board
Factory Assembled
and Tested

International Microcomputer
Corp. Capacative Key-
board Assembled and
Tested w/enclosure

TDL Software on Cassette or Paper Tape 20% Off List

SPECIAL
LIST CASH

PRICE PRICE

555

169

Check Our Prices On:

Cromemco, Vector Graphic, Mullen, Digital Systems, Centronics,

Sanyo, Hazeltine, Computalker, IMSAI, ECT, IMC, North Star, Trace

Plus Most Other Major Lines.

Subject to Available Quantities. Prices Quoted Include Cash Discounts. Shipping and Insurance Extra.

Bus...S-IDQ,inc.

Address. . .7 White Place

Clark, N.J. 07066
Interface. ..201-382-1318

S60

440

144

123

TH€ CQMPUTCR CORM€R C28

White Plains Mall, Upper Level

200 Hamilton Ave.

White Plains NY 10601

Phone: (914) WH9-DATA

Near Bronx River Parkway &
Cross Westchester Expressway.
Plenty of parking.

"The S100 Bus stops at
White Plains" with one of
the largest collections of boards
compatible with the Altair Bus
(also IMSAI) in the greater NY
area.^

You've read about the
Sol-20, now come up and
see it. We carry Processor Tech,
Polymorphic, IMSAI, North Star,
TDL, Blast Master and Pickles
and Trout.

GOOD PRICE AND SERVICE

10-6Mon.-Sat.

Thurs. till 9

C-28

TH€ COMPUTCR CORMCR

SUPPLIES

• FLOPPY DISKS, MINI OR
STANDARD MEMOREX OR 3M

• 3M DATA CARTRIDGES
DC300A. DC100A

• 3M DIGITAL CASSETTES

• 3M OR MEMOREX AUDIO
CASSETTES, C 60

• 3M DISK CARTRIDGES

WE OFFER:

•COMPETITIVE PRICING

•IMMEDIATE DELIVERIES
(Any Quantity)

• UNCONDITIONAL GUARANTEE

BETA BUSINESS SYSTEMS

8369 VICKERS ST., *G
SAN DIEGO, CA 921 1 1 , ^ — ,
(714) 565-4505 €H

B39

RELIABLE APPLE SOFTWARE

NOW AVAILABLE ON CASSETTE

AM programs are written in Integer BASIC & run in 16K
unless otherwise stated.

1.
2.

6.
7.

Rainbow's Pot-of-Gold, Vol. 1,- 49 BASIC programs
Microchess Graphic display, beginning to intermediate,
Machine language and BASIC

3. Inventory • Holds approximately 140 items in 16K

4. Income Tax 1040, Schedules A&B. requires 20K &
Applesoft 1

5. Morse Code Trainer Variable speed 1-100 wpm.uses Apple-
soft 1

Appletalker Gives your APPLE a voice, machine language
Speed Reading, Vols. 1-4, four programs designed to improve
your reading speed
Galactic Battle - Low resolution, real time space battle

9. Apartment Building Investment Analysis - Analyzes the
investment potential of an apratment building
Microproducts Assembler Apple assembler machine language,
uses 4 K

Devils Dungeon - Exciting adventure game
Appleodian - Irish jig composing algorithm

13. Hi- Res Life - Conway's original Game of Life, machine
language, requires 24K

14. Applevision ■ High resolution graphics and music demo, machine
language and BASIC

Blackjack One or tvw players in low-res graphics,
machine language and BASIC
Apple Checkbook Complete checkbook balancing
and reconciliation program

Software is available on disk for media charge of SS.00
Send Check or Money Order, sorry no C.O.O., to:

RAINBOW COMPUTING INC.

10723 White Oak Ave., Dept. K.L.
Granada Hills, CA 91344
(213) 360 2171

R12

California Residents add 6% sales tax
Allow 3-4 weeks for delivery

$49

15
35

40
15

15
20

10
10

argains

IMSAI et al

MARKETLINE SYSTEMS, Inc.

2337 Philmont Awe. M17
Huntingdon Valley, Pa. 19006
215/947-6670 • 800/523-5355

save more than 20/ !
NORTH STAR HORIZON

The smartest computer at the smartest price.

Horizon-1 kit, list $1599 $1279

Assembled & tested, list $1899 $1519

Horizon-2 (2 drives) kit, list $1999 $1599

Assembled & tested, list $2349 $1879

Datapoint Terminal, list $814 $650

Printec-100-cps Printer, 1 5" paper, 100 characters
per second, tractor feed, interfaced for North

Star, list over $3000 $1500

Yes, you can get a complete North Star business

system for only $3429

plus shipping.

2 interconnecting cables $50

or free schematic to make your own for less
than $10 worth of material. NC res add 4% tax

We have business software, too. These printers
do IBM quality work. Only 60 available, so hurry.
You can make money with this complete
business system. Sample printout, SASE.

AMERICAN

SQUARE
COMP UTERS A66

KIVET DR#JAMESTOWNNC 27282
(919) 883-1105

PROFESSIONAL SOFTWARE

GENERAL LEDGER FEATURING:

*Multlple Debit-Credit Entries
*Comment Field
*Security Check
*Extensive Error Checks
*User Oriented - with manual
*Many Additional Features

System Requirements: 8K Free
Memory, North Star Basic (CP/M
available soon), Specify 1 or 2
Drives. Price: $50.00

Ask about our other business,
educational and scientific soft-
ware.

ECOSOFT

P.O. Box 68602

Indianapolis, IN. 46268

E34

Video Monitors

(9" size, dual jacks)
RCA (550 lines resolution). . $159.00

SANYO (600 lines resolution) . $169.00

Supercrisp GBC (700 lines) $180.00

(no fuzzy screen corners on this CRT.)

Other sizes available. Free connector on all
orders. Free 25-foot coax cable with connectors
for two-station looping on orders of two or more
units ($10.00 worth)

Ready-to-Plug-in

Z-80 Computers (Quay) with:

Monitor in ROM, 1K Static RAM, 3K PROM sockets,
onboard PROM Programmer, RS232 (TTYyParallel
keyboard interface, MainFrame (18 amps, 12-slot
Mother Board with connectors and guides, front-
panel switches for On/Off, Reset, PROM Program,
8K Static RAM Board (socketed); all housed in an
attractive woodgrain/aluminum cabinet).
All for $937 (regular, $1,080). All prices include ship-
ping. NY residents add tax.

Send money order or check to:
"** C.E.T. Systems ~~

509 Cathedral Pkwy 10-A New York NY 10025
Call Tues-Sat. (212) 663-0789 for more info egg

S-ioo 11 Slot & others

Card Cage

For 8300 Motherboard

$34.50

m Post Paid m
USA *

Complete with Edge Guides

And Hardware

Dealer Discount Club Refund

MM Keith & Co

P.O. Box 954
Racine Wisconson 53405

K15

X TRS-80 y

SPECIAL PROMOTION SALE

Save 10% plus, NO TAXES will
be charged on out of state ship-
ments. Units Delivered in Continen-
tal U.S.

You can also save 10% on other
fine Radio Shack® products we
carry.

Offered exclusively by

Radio Shack® ™*
Authorized Sales Center

1117 Conway, Mission, Texas 78572
Radio Shack® warranties will be
honored by your local Radio Shack®

store. (512) 585-2766

vtsa'

124

NEW YORK CITY

and

LONG ISLAND

IF YOU WANT PROFESSIONAL SERVICE

IN A CASUAL ATMOSPHERE . . .
AND A LARGE VARIETY OF EQUIPMENT

BUSINESS APPLICATIONS

General Ledger, Inventory, Accounts Payable,
Accounts Receivable, Word Processing Systems.
GENERAL APPLICATIONS

Northstar Macro Assembler $65

Northstar Mailing Label Program $45

STOCK MARKET PACKAGE (Unique) Makes
Makes Ticker-Tape Obsolete.
Send $2.00 for descriptive brochure on Stock
Market Package.

BYTE SWOP

B14

THE AFFORDABLE COMPUTER STORE

T.M.

130 East 40th Street

New York, NY 10016

(212)889-4204

(Corner Lexington Avenue)

Tues. thru Fri. 11 to 7 • •

Saturday 10 to 5* ■ ■ •

2721 Hempstead Turnpike

Levittown, NY 11756

(516)731-8116

(Just East of Wantagh Pkwy)

12 to 8

10 to 5

TRS-80
SOFTWARE

THE ELECTRIC PBICIL WORD PROCESSOR - $99.95

ELECTRIC PENCIL, highly respected as a superior word processor for home
computers and small businesses, is now available for the TRS-80 computer!
In addition to all standard ELECTRIC PENCIL features (free format entry,
line and character insertion and deletion, forward and reverse scrolling
with speed control, string search, coded search, search and replace, block
moves, inserts, and deletions, fully formatted print contol, page titling
and numbering, etc., etc.), the TRS-80 version offers the following
features: transparent cursor, two-key rollover, repeating keyboard,
uppercase only in unmodified TRS-80' s, or upper and lowercase entry and
display after simple modification (documentation included) .

THE ELECTRIC PENCIL runs printers using Radio Shack's expansion interface or
will operate any RS-232 300 baud printer using our TRS232 printer interface.
Either LEVEL-I or LEVEL-II 16K computers may be used! THE ELECTRIC PENCIL
opens a whole new world of practical applications for the TRS-80 computer!

RSM-1S: A MACHINE LANGUAGE MONITOR FOR THE TRS-80 - $23.95

NEW! RSM-1S IS NOW AVAILABLE GN FLOPPY-DISK FOR $29.95! ! KSM-1S provides
you with 22 commands which interact directly with the Z-80 processor in your
TRS-80. You may examine your ROM's, test your RAM, enter and execute
machine language programs, read and write machine language tapes, and much
more! A SYMBOLIC DUMP command disassembles object code and displays it as
Zilog standard Z-80 mnemonics! Memory may be displayed in HEX or either of
two ASCII formats, and can be EDITED, MOVED, EXCHANGED, VERIFIED, FILLED,
ZEROED, TESTED, or SEARCHED for one or two-byte codes. Memory display
commands may be stepped with SPACE, or aborted with BREAK. Runs in 4K.

AIR RAID; A REAL-TIME TRS-80 SHOOTING GALLERY! - $14.95

AIR RAID is a game where large and small airplanes fly across the screen at
different altitudes. A ground based missile launcher is pointed and fired
from the keyboard. Missiles may be guided after launching! Aircraft
explode dramatically when hit, sometimes destroying other nearby planes!
Score is tallied for each hit or miss, and the highest score is saved to be
challenged by other players. Play ends when time runs out, but extra time
may be earned with a high score. AIR RAID provides hours of fun for you,
and is a super demonstration program for entertaining friends! Runs in 4K.

All software shipped postpaid with LEVEL I and LEVEL II versions on the same
cassette. Add shipping for hardware items. (Calif, residents add 6% tax) .

S51

* SMALL SYSTEM SOFTWARE * P.O. BOX 366 * NEWBURY PARK, CALIF. 91320 •

MICRODESK

The perfect home
for a personal or business computer

MICRODESK M 39.50

48" x 24" x 26", Shelves 23" x 23", One adjustable.
See it at your computer store or order it from:

COMPUTER SYSTEMS DESIGN

906 N. Main Wichita, Kansas 67214

DEALER INQUIRIES INVITED

TRS-80
HARDWARE

TRS232 PRINTER INTERFACE - $39.95 (Assembled and Tested)

The TRS232 is a self-contained software-driven output port. Cassette
software and source listings for driving printers from LEVEL-II BASIC or
machine language programs are furnished. Diablo printers, Teletype Model
43, TI Silent, or any RS-232 printer may be used with the TRS232. A 20-mil
current loop output drives model-33 110 baud teletypes. The TRS232 is small
(about 1" x 2" x 3") and installs in series with the power and cassette
cables on your TRS-80 computer (all cables and connectors are furnished) . A
standard DB-25 connector mates with the printer cable. The TRS232 may be
left in place at all times, since it does not interfere with cassette
operation. THE ELECTRIC PENCIL uses the TRS232, thus both word processing
and BASIC program listing and documentation are supported!

PARA-PORT: 2 1/2 PORT PARALLEL I/O BOARD - $79.95 (KIT)

Our parallel port board can be used for driving LED light displays, reading
external keyboards, polling sense switches, driving parallel port printers,
controlling relays for lamps, sprinklers, or any place where control of
external devices is desired! The TRS-80 can now control something besides a
cassette recorder! The board contains two full 8-bit input and output
ports. It features 8212 input latches which automatically generate the
necessary status information when new data is input. Output strobes are
generated and there is a third 4-bit status port so that full handshaking
protocol may be established. Requires external 5-volt power supply.

40/44-1; SINGLE-SLOT ADAPTER - $24.95 ($19.95 with PARA-PORT)

Consists of a small adapter board, 40 pin edge connector, 44 pin socket,
power supply connections, support feet, and a 40 pin ribbon cable to connect
to the TRS-80 expansion port. Operate any of our boards, or use any 44-pin
board to do your own thing! A trade-in allowance will be offered to upgrade
to our six-slot buffered mother board.

OTHER TRS-80 PRODDCTS

CHESS: $19.95 Microchess 1.5 plays a good game of chess, uses graphics.

RSL-1: 14.95 Draw patterns on your screen then play the game of LIFE.

ESP-1: 29.95 Editor, assembler, and monitor using INTEL 8080 mnemonics.

LST-1: 7.95 A disassembled listing of LEVEL-1 BASIC with some comments.

SCM-1: 4.95 A fully detailed schematic of the TRS-80 microcomputer.

CVR-1: 3.95 Quality dust covers in cloth-backed vinyl to protect your
keyboard. Colors: Spanish Red, Antique Ivory, Rich Brown.

* SMALL SYSTEM BARDMARE * P.O. BOX 366 * NEWBURY PARK, CALIF.

91320

125

TRS-80

Micro-Mega CASSETTE CONTROL UNIT

r^ S r ed " P > "" r ***!** Ia l n ' l ""«m • Pinpo.nr program
locations on lape with an auilihlc auxllian monitor . (,ol

protection from recording ami p| a> Lack diklu-s resulting from

of recorrrcabl'es """' *" ^^ *"* a ' u1 u "P*»«ing

I lie Micro Mega Cassette Control
I ml does all this anil more You
get instant manual control of the
recorder at the flick of a switch
Wini to find the beginning or
end of a program' Hick another
iwilch. and m.u II hear it. All
cables remain plugged in all the
time

I he Micro Mega ( assette Control
I nil does | lot to clean up and
nealeii up sour whole TRS-80 in-
stallation too As shown at the left.
. i's in a :':"\>' box which snuggles

between the ke> board and sour recorder F here is no need
to move the recorder. .,iul there no longer are any 90 degree
cable bends whipping around It s last, neat and convenient and
Ms \ ■ bargain!

CAMCTTSCONTMM l MI-U2.5*

New Software:

INTELLIGENT MICRO-MOUSE ?

**!. ' he Punsts argue whether this programmed graphic-
mouse has true artificial intelligence \nvwav it's certainly
not a stupid mouse, and certamlv it s a persistent mouse. Its able
to lind an escape route Irom any starting point within a 20-ceU
ma/e. and having escaped, it's able to find its way back into the
ma/e. three separate variations of "Micro-Mouse" are provided
on a cassette Each of them runs under Level I Basic in 4K of
memory.

Ml< KOMOI SK -$10.00

M icro - Mega

P.O. BOX 6265 • ARUM, ION. \ \ ziiOt,

M54

AD-68A ANALOG-TO-
DIGITAL CONVERTER

• 8 analog input channels

• Occupies one SWTPC 6800 I/O
slot

• Quality components and PCB

• Complete documentation
•90 day full warranty
•Assembled and tested

$39.95

(Virginia rr-idrnts add 4«o talcs tail

Available from your local dealer or
factory direct. Write for additional
information.

Innovative Technology

124

510 Oxford Park

Garland, Texas 75043

(214) 270-8393

SOL-20
SOFTWARE

from ESV Computer Service

Processor

DIAGNOSTICS II: Checks user RAM (addresses are keyboard selectible by operator), video RAM, SOLOS or Boot-
load RAM, audio interface, and personality module. Features hard-copy printout of video displays using TAB key, and
selectible output ports. Cassette tape comes with SOLOS version on one side & Bootload (BOOTL) on the other for use
with either cassette or Helios SOL Systems $50. on cassette

DISASSEMBLER: Allows conversion of machine language programs to assembly language Features operator
selectible output ports for hard-copy printer or video display and audio cassette storage of disassembled text Permits
modification to be made fa custom use or possible relocation. Symbol table may be anywhere in RAM and is assigned
by the operator during initialization Line numbers and labels are automatically assigned by the disassembler during
construction of the assembly language program Special characters will be displayed in the line number s most sig-
nificant digit to flag the need to divide the machine code for 2 or more passes when the line number exceeds 9999 Tape
storage (if selected) is done byte-by-byte (text) for use with assemblers other than ALS-8 or Software #1
$30. on cassette

MAILBOX: A mailing list program designed to work on your Helios Disk System. Features online editing for data
entry, operator may select serial or parallel drivers (included on diskette) for hard copy, presorted mailing labels (by zip
codes as required by postal regulations for bulk mailing), label search, modification of single line should address or
name need changes, file status check to determine amount and percentage of dead space and number of names in
file, file compression to remove data in the same size file, generate separate diskette to increase data storage, will
dump files to either 2 or 4 columns on printer, and is operator selectible $45 on Helios diskette

DROIDS: An action game where you play the computer. Try to escape Droids by hiding behind fences. Features
static practice mode for skill development and real time attack mode with selectible difficulty factors
$1 9.50 on cassette

ALS-8 UTILITIES adds cassette I/O operations to ALS-8 In-
cluded are seven custom tape commands and five clear
memory commands Source program on cassette will
assemble into 12C (hex) bytes
EC-001 Source program on cassette tape $15.00

S0FTPAC #1 cassette uses Basic/5 on any Sol-20/SOL0S
with 16K of RAM Included are four games. STAR BLACK-
JACK, CRAPS, and WAR
EC-002 Basic/5 programs on cassette tape $18 00

BLOCKADE is an action game for two players on the same key-
board Build a wall as you move and trap your opponent Get
sound effects through an AM radio or the Music System
Machine language program runs in 8K of RAM
EC-003 Machine language program on cassette $14.00

S0L-20 DIAGNOSTIC checks user RAM. system RAM.
SOLOS, keyboard, video, and cassette interface This
machine language program requires 8K of RAM
EC-004 Machine language program on cassette $45.00

CALENDAR & TIME has a calendar for whatever month and
year you want Also included is a time program which displays
hours, minutes, and seconds on the screen These Basic/5
programs require 16K of RAM
EC-005 Basic/5 programs on cassette tape $10.00

DIRECT REDUCTION LOAN provides amortization schedule
for entire loan period or a single period of interest Total
interest paid is also calculated 12K of RAM is required for this
Basic/5 program
EC-006 Basic/5 program on cassette tape $10.00

ACCOUNTS RECEIVABLE uses cassette data files to keep cus-
tomer information on cassette tape Functions include update,
report, search, and enter new records 20K of RAM and 2
cassette recorders are required to run this Extended Cassette
Basic Program
EC-007 Basic program on cassette tape $25.00

SMARTMOUTHED BLACKJACK uses Las Vegas rules includ-
ing split hands, double down, and insurance bets The
humorous wise-cracks of the dealer keep the attention of the
player for hours This Extended Cassette Basic program re-
quires 32K of RAM
EC-008 Basic program on cassette tape $19.50

BIORHYTHM cassette produces complete plot or a simple list
of critical days Output can be directed to any pseudo port
Extended Cassette Basic version requires 24K Basic/5
version requires 16K Any number of days can be forecast
EC-009 Basic/5 program on cassette tape $19.50

EC-0 10 Extended Cassette Basic program cassette $19.50

IMMEDIATE DELIVERY!

All items shipped from stock. First generation recordings.
One Year Warranty!

All above items on 1200 baud CUTS cassette,

All orders COD or prepaid Alow 3% for freight if prepaid Texas residents add 5% sales tax Write for catalog Dealerships available

COMPUTER P-^RT

C80

926 N. Collins • Arlington, TX 76011 • (817) 469-1502

BUSS F4

OnAcfiejuUnt <zN twiUtUx of cHcakh Co. ComfxuUn.
325 PENNSYLVANIA AVENUE. S.E.
WASHINGTON. D. C. 20003
Dear Kilobaud reader:

Buss lets you in on news of H8- and Hll-
compatible hardware and software from
other vendors as well as providing in-
formation on new items being developed
in Benton Harbor before their official
announcement. It also shares the exper-
iences of users with their computers and
peripherals from Heath Co. All this can
help you plan additions to your system.

Your 12-issue subscription can start
either with the current issue or with
all available back issues. Send $ 7.45
to Buss, 325 Pennsylvania Ave., SE,
Washington, DC 20003.

CHARLES FLOTO editor

Full ASCII Professional
Keyboard Kit, Model 756

• Full I 28 Character ASCII • Tri-Mode MOS En-
coding • MOS/DTL/TTL Compatible Output •
Two-Key Rollover • Level and Pulse Strobe •
Shift and Alpha Lock • Selectable Parity •
Positive or Negative Logic • All New. OEM
Grade Components • Gold Contact, Low
Bounce Key Switches • Rugged G- 1 Printed
Circuit Board • Low Power Consumption . . .
and More

Model 756 Keyboard Kit $64.95

Model 701 Plastic Enclosure $14.95

Model 702 Steel Enclosure $29.95

Send for catalogue of other NEW merchandise,
Semis, Sockets, ICs, Res., Caps, and MORE.

N.Y.S. Residents Add 4% Sales Tax

Send to: Key Electronics
P.O. Box 3506
Schenectady, NY 12303 K14

RADIO SHACK/TRS-80

16K MEMORY PACKAGE

This package includes all that is neces-
sary for a very easy expansion of the
memory 4K to 16K bytes. All you have
to do simply is: take the 4K Chips
out and plug in new chips in the same
sockets. No soldering! Simple, easy-to-
follow instructions! User-tested. Kit con-
tains eight 250nS Dynamic RAM Chips,
2 plug-in DIP Shunts and a complete
set of instructions. Expansion Unit Own-
ers can fill empty sockets with 16K
or 32K RAM. It is easy! It is fun! It is
a smart way to save money!

No. 786-R 16K RAM Package $129.95
No. 786-Z 32 K RAM Package $310.00

DELTRONIKS D28
P. O. Box 29363
Atlanta Ga 30359

IZZZ— (404) 458-4690 _— —

126

WlBtH Si mBU BHBHIBW

I Problems

s^i

S Not with PX **!*£

£2 Certified Cassettes! c •

PX Corporation offers professional cassettes

designed specifically for the personal

computer market.

100% tape certification... for error-free tapes; no

drop-out

Tested thoroughly... for high frequency response;

low noise; high-den-
sity recording

Magnetic leader... for instant recording; cuts load-

ing problems!

Delrin rollers... for better tracking; less tape wear;

uniform speed

Graphite-impregnated polyolefin washer... for less

drag & wear; imper-
vious to humidity

Spring/felt pressure pad... for positive low-friction

tape-to-head contact

Screw-type housings; welded plastic window...

for dust-free operation

To introduce you to our
quality cassettes, for a
limited time, we are
offering a free Cassette
storage unit with any order
of 1 cassettes

Holds 20 cassette boxes

FREE!

with any order of 10 cassettes

PX/Corporation P40

P.O. Box 16408

San Antonio. Tx 78216

If using Visa or Master Charge,
please include the following:

^Expiration Date

VTSA

Card ho

Signature

PLEASE SEND ME:

D 1 cassettes in free storage unit pictured above $27.50
D 5 cassettes in plastic MORELCO-style boxes $13.75

□ Cassette Carousel (as above, without cas-

settes) $ 8.75

□ Cassette storage center (holds 72 cassettes;

36 in boxes (hot pictured) $15.00

□ Certified diskettes in a box of 1 (Specify IBM.

Shugert or Memorex compatible) $59.50

Sub Total $
Texas residents add b% sales tax $
Shipping & handling
TOTAL AMOUNT TO BE ENCLOSED $

$1.50

Name

Address
City

State

.Zip

EhJ

OUR VISIBLE MEMORY ADDS FUNCTION

AND FUN TO YOUR 6502

This DOT MATRIX display board doubles as an 8K MEMORY. You can use it as a
display, memory expansion or both with graphic and text display software
available. You get high resolution graphics with no wait states, no snow, and no
processor overhead. K-1008 ASSEMBLED and TESTED $289.00, BARE BOARD
$40.00 K-1008-1 GRAPHIC/TEXT UTILITY SOFTWARE LISTING $20.00.

For charts and graphs, it is
valuable in the educational,
research and business fields.
Shown to the right is a single
period of a complex frequen-
cy waveform and its frequen-
cy spectrum chart.

fllCSO TtQesXWY UM.1MTO VISlsYX '
FOB TIC KIH-I HtaWOTTUTtH

You have just eitnessed the hio> resolution arsenic
capabilities of the KHI Visible heeory . tut, it lln
display* text oith uuir« versatility! Thi« text
display subrout ina displays 18 I inas of 33
I noii case characters oith true dasc
routine using, SB* 1 1 caps (or loser case attains U
lines' Subscripts and superscripts can also be dis-
played for oath equations. „>

t 320

bytes
eory expansion to the Kin
t Srapnics and text display soft
t Ask Dave or Hal for en *
• fteoular price 929*}. f~

avail

i an the <m

HI'

Graphics allows you to pro-
gram games with much more
accurate representation of
your game because YOU
DETERMINE THE SHAPES
on the display, not a ROM
character generator. Our
LIFE program allows tremen-
dous creativity in creating
complex colonies for obser-
vation of generation growth
and decay.

As a dot matrix formatted 200
high by 320 wide, it allows
high resolution patterns to be
displayed and evaluated. It
enhances system perfor-
mance for data acquisition
displays, math equation plot-
ting, etc.

For text display, dot matrix is
the ultimate. Any character
set the user desires is possi-
ble. Even subscript and
superscript in the same col-
umn, and— mixed text and
graphics. The improved man-
machine interface for an un-
skilled operator increases
productivity.

Developed by a leading group of New England engineers for interface with the
three 6502 KIM BUS systems (KIM, VIM, AIM). The K-1008 requires only the pro-
cessor card and its power supply to function as a memory. Add a monitor and
you have graphics and text display available. Micro Technology also makes
K-1000 Power Supplies, K-1005 Card Files, K-1002 8 Bit Music Systems (with ad-
vanced software), K-1020 Regulated Wire Wrap card, K-1012
IO/COMM/PROM/2708 Programmer card, K-1016 16K Memory, all sold assem-
bled and tested or as bare boards. Write for technical information, prices and
terms.

Micro Technology Unlimited

P.O. Box 4596

Manchester NH

03108 M44

jr^

127

From the people who brought you KIMSI —
Mr. Interface™ does it again with...

BETSI

The PET* to S-100 bus
Interface/Motherboard

I Expand your PET as easily as S-100 users !

• Plugs directly into any PET, no cable fabrication or additional connectors required.

• Compatible with virtually all S-100 boards (including memory and I/O types).

• Does not slow the CPU or alter PET's operation in any way.

• Does not interfere with PETs IEEE or parallel user ports.

• Interface draws only lOOma at 8V.

And Betsi includes:

• On -board Dynamic Memory Controller for the S.D. Sales "Expan do-ram" high density/low
power memory board (expand PET's memory to the limit on a single S-100 card)!

• Onboard sockets and decoding circuitry for 8K of PROM (add future PET firmware without
purchasing an S-100 PROM card).

Now available from stock at a price that can' t be beat ( even just for memory expansion) !

BETSI Interface/Motherboard - Kit $119, Assembled $165
Expandoram 24K memory board - Kit $364, Assembled $414

See your local dealer or contact FORETHOUGHT PRODUCTS

* PET h a Commodore product

Coburg Box 8066; Coburg, OR 97401 ™
(503) 485-8575

AROUND

THE I MII'STKY

(from page 7)

warehouse store in Garden Grove
CA and our late-fall-opening
shop in Chicago's Water Tower
Place as two sites for Computer
Centers within Radio Shack
stores. We are also considering
converting some existing Radio
Shack stores to Computer Cen-
ters in order to hasten the day
when we are truly nationwide
with this project." Capital expen-
ditures for the 50 centers are ex-
pected to total about $4 million.

Several executives have been
named to key positions in Radio
Shack's computer organization.

Ted. F. Cromer, formerly gen-
eral manager of Tandy Comput-
ers and a veteran of 13 years with
IBM, has been selected as direc-
tor of Radio Shack Computer
Centers. He will be assisted by the
Radio Shack district manager in
the area of each center.

Jon A. Shirley, who has been
with the company since 1958 in a

variety of merchandising func-
tions, most recently with their
overseas operation, has been
named director of Radio Shack
computer merchandising, a
newly created position.

Carroll B. Ray will be director
of computer applications, an-
other new position chiefly con-
cerned with the development and
acquisition of TRS-80 software
programs. Ray, who joined Tandy
Corporation in 1964 and was
named Radio Shack vice-presi-
dent/controller in 1970, has been
involved in the area of corporate
development for the Radio Shack
division.

According to Kornfeld,
"Within each Computer Center
we expect to see at least one sales
manager with extensive computer
experience, a technician and cler-
ical help." He added that
"several hundred new job open-

ings have been created by the
launching of the program, and in
addition, Radio Shack's Fort

Worth computer factory contin-
ues to expand in people and
space."

CORRECTIONS

Carl A. Wall of Willowdale, Ontario Canada, writes: Loaded the
program in the article "It's Here: Cook's Memory Test" (July
1978, p. 70) in my SOL-20 and it did not work. The problem was
traced to the call statements in program B. These should be
changed to the following to work with SOLOS version 1.3
(released 77-03-27).

Address

Op Code

C993

CD 19 CO

C997

CD E8 C3

C9A0

CD 19 CO

The following replacement lines were sent to us by the authors
of "(Con)text Editor" (September 1978, p. 22) too late to incorpo-
rate into the article.

710 CL0AD*LCL0AD*F:F0RI = 1T0Q:T$ = —

720 FORI = 1TOQ:B(F(l)) = l:NEXT:B(U) = 0:B(UN) = 0:F(0) = 0:B(0) = 0:L(0) = 0:GOTO25

760 L(0) = U:CSAVE # L:F(0) = UN:CSAVE*F:FORI = 1TOQ:J = LEN(L$<I)):IFJ =0THEN780

1100 K = LEN(T$):FORJ = PTOLEN(l$):IFMID$(l$,J,KK>T$THENNEXT:R = 1:RETURN

1101 IFLEN(l$) = 0THENI=0

1102 P = J + K:R = 0:RETURN

128

THE INCREDIBLE LEARNING MACHINE

WHATSIT.

(Wow! Howd All ThaL&uff^et InThere?)

• She's a Conversational Query System!

• She's an Indexing/Filing System!

• She's a 'Data Base Manager' for your Microcomputer!

"One of the first software products of the
New Computer Age ..."

-Ted Nelson, author of
Computer Lib/Dream Machines

Mail to:
123

Information Unlimited
331 W. 75th Place, Suite 2-I
Merrillville, Indiana 46410
219- 769-9280

D Model CP-1 for C-Basic (requires 40K RAM) $125

D Model NS3 for North Star Basic (requires 24K RAM) $75

D WHATSIT Manual $25

D Quantity discount schedule for Dealers.
D More information (I'm running disc BASIC

on a computer)

computer)

A CREATION OF

'OTOOTGR MCAOWte™

EPROM PROGRAMME!
8PEAK8 FOR IT8ELFI

M31

U2708 Utility In EPROM S 29.95

All software routines necessary to test, burn, verify and copy 2708s using the
B-08 Programmer

DEPT. K, P.O. BOX 1UO, DEL MAR, CA 92014 (714) 756-2667

PRIC€ DR€ A KTHROUGH ! !

lOO TRS-80 LEVEL II PROGRAMS
$49.5 O Cor ALL lOO programs

5 cassettes— from the first mass marketer of ready to load software.

Quality In Quantity— a value In excess of SSOO.OO (Check the price per program In
other ads.)

For the first time there are enough users of a single type of computer to justify mass
marketing of high quality, ready-to-load programming. We are only able to market
at this price because WE EXPECT TO SELL A GOB OF THEM

Available for Immediate delivery. Buy now II Volume only will allow us to continue
marketing the LIBRARY 100 at the $49.50 price.

US— BUSINESS AND FINANCE. Moving ad, Sales-Cost Margin, RE Investment

Analysis, Interest Determination, Depreciation, and 19 more.
IS— GRAPHICS. Advertisement, Red Baron's Enemy, Fireside, Blocks, and II

more.
15— EDUCA TION. 5 Math, and 10 subjects.
15— HOME. Nutrition, Xmas List, Travel Mileage, Shopping List, and II more.

30— GAMES. S T , Tiger Shark, Memory Quiz, Stingray, and 26 more.

100 programs which cost you 49.5 cents a piece!

The Greatest Bonus of all (free with order) TINY PILOT. No, TINY PILOT does not fly
small airplanes, it is the first new language for your TRS-80. With |ust 6 of Its com-
mands even a child can be programming in minutes.

Call (404) 939-603 1 to order. 24 hour service.
5% discount on Deltronlcs memoryl

The Bottom Shelf, Inc.
P.O. Box 49104
Atlanta, Georgia 30359

: a :

NOT A KIT

8v^/ 15A, ± 16v(// 3 A power

Rack mountable

15 slot motherboard

Card cage

Fan, line cord, tuse,

switch, EMI filter

Desk top version option

8vf<7 30A, ± / \6v((i 10A option

voltage monitor option

100 pin connectors optional

Rack
mounted
model From
$200

Desk
top model
From $235

Write or call for a copy of our

detailed brochure which includes

our application note

BUILDING CHEAP COMPUTERS.

INrEGR4ND „„

8474 Ave 296 • Visaha. CA 93277 • (209) 733 9288
We accept BankAmencard/Visa and Master Charge

129

COMPUTER INTERFACES & PERIPHERALS

For free catalog including parts lists and schematics, send a self-addressed stamped envelope.

APPLE II SERIAL I/O
INTERFACE *

Part no. 2

Baud rate is continuously adjustable
from to 30,000 • Plugs into any periph-
eral connector • Low current drain. RS-
232 input and output • On board switch
selectable 5 to 8 data bits, 1 or 2 stop
bits, and parity or no parity either odd or
even • Jumper selectable address •
SOFTWARE • Input and Output routine
from monitor or BASIC to teletype or other serial printer.
• Program for using an Apple II for a video or an intelli-
gent terminal. Also can output in correspondence code
to interface with some selectrics. Board only — $15.00;
with parts — $42.00; assembled and tested — $62.00.

MODEM

- m» *j

iT^P^

Part no. 109

• Type 103 • Full or half
duplex • Works up to 300
baud • Originate or Ans-
wer • No coils, only low
cost components • TTL
input and output-serial •
Connect 8 ohm speaker
and crystal mic. directly to board • Uses XR FSK
demodulator • Requires +5 volts • Board $7.60;
with parts $27.50

DC POWER SUPPLY*

Part no. 6085

• Board supplies a regulated +5 volts
at 3 amps, +12, -12, and -5 volts at
1 amp. • Power required is 8 volts AC
at 3 amps, and 24 volts AC C.T. at 1 .5
amps. • Board only $12.50; with
parts excluding transformers $42.50

JBP aum%

TAPE INTERFACE *

Part no. 111

• Play and record Kansas
City Standard tapes •
Converts a low cost tape
recorder to a digital re-
corder • Works up to 1200
baud • Digital in and out
are TTL-serial • Output of
board connects to mic. in
of recorder • Earphone of
recorde r connects to input on board • No coils •
Requires +5 volts, low power drain • Board $7.60;
with parts $27.50

T.V. TYPEWRITER

Part no. 106

• Stand alone TVT

• 32 char/line, 16
lines, modifications
for 64 char/line in-
cluded • Parallel
ASCII (TTL) input •
Video output • 1K
on board memory •
Output for compu-
ter controlled cur-
ser • Auto scroll •
Non-destructive curser • Curser inputs, up, down, left,
right, home, EOL, EOS • Scroll up, down • Requires +5
volts at 1.5 amps, and -12 volts at 30 mA • All 7400, TTL
chips • Char. gen. 2513 • Upper case only • Board only
$39.00; with parts $145.00

TIDMA

Part no. 112

• Tape Interface Direct Memory Access • Record
and play programs without bootstrap loader (no
prom) has FSK encoder/ decoder for direct con-
nections to low cost recorder at 1200 baud rate,
and direct connections for inputs and outputs to a
digital recorder at any baud rate. • S-1 00 bus com-
patible • Board only $35.00; with parts $110.00

UART & BAUD RATE
GENERATOR*

'•feu

Part no. 101

• Converts serial to parallel
and parallel to serial • Low
cost on board baud rate
generator • Baud rates: 110,
150, 300, 600, 1200, and
2400 • Low power drain +5
volts and -12 volts required

• TTL compatible • All characters contain a start bit, 5 to
8 data bits, 1 or 2 stop bits, and either odd or even parity.

• All connections go to a 44 pin gold plated edge connec-
tor • Board only $12.00; with parts $35.00 with connector
add $3.00

LL.

8K STATIC
RAM

Part no. 300

• 8K Altair bus memory •
Uses 2102 Static memory chips* Mem-
ory protect • Gold contacts • Wait states • On
board regulator • S-1 00 bus compatible • Vector
input option • TRI state buffered • Board only
$22.50; with parts $160.00

RF MODULATOR

Part no. 107

• Converts video to AM modu-
lated RF, Channels 2 or 3. So
powerful almost no tuning is re-
quired. On board regulated
power supply makes this ex-
tremely stable. Rated very
highly in Doctor Dobbs' Journal. Recommended
by Apple. • Power required is 12 volts AC C.T., or
+5 volts DC • Board $7.60; with parts $13.50

RS 232/TTY *
INTERFACE

Part no. 600

• Converts RS-232 to 20mA
current loop, and 20mA current
loop to RS-232 • Two separate
circuits • Requires +12 and -12
volts • Board only $4.50, with
parts $7.00

past *& €i>0

WKb

RS 232/TTL*
INTERFACE

■*■•■■ 4_,a»3>Ji — uM

* ~&t#&

Part no. 232

• Converts TTL to RS-232,
and converts RS-232 to
TTL • Two separate circuits

• Requires -12 and +12 volts

• All connections go to a 10 pin gold plated edge
connector • Board only $4.50; with parts $7.00
with connector add $2.00

ELECTRONIC SYSTEMS De Pt- KB < PO - Box 2163 8, San Jose, CA. USA 95151

Th OrrtOr ■ Mention P art number and description. For parts kits add "A" to part number. In USA, shipping paid for orders accompanied by check, money order, or
IV/ wl Uwl ■ Master Charge, BankAmericard, or VISA number, expiration date and signature. Shipping charges added to COD. orders. California residents add 6.5%

for tax. Outside USA add 10% for air mail postage, no C.O.D.'s. Checks and money orders must be payable in US dollars. Parts kits include sockets forall
ICs, components, and circuit board. Documentation is included with all products. All items are in stock, and will be shipped the day order is received via
first class mail. Prices are in US dollars. No open accounts. To eliminate tariff in Canada boxes are marked "Computer Parts." Dealer inquiries invited.
24 Hour Order Line: (408) 226-4064 * Circuits designed by John Bell

master chstge

4804 STATIC, TTL IN OUT 1024x4 N-MOS RAM

GENERAL
DESCRIPTION

Part Number 4804
isa4K semicon-
ductor random
access memory

organized as 1024 4-bit words. It is fully static and
needs no clock or refresh pulses. It requires a
single 5 volt power supply and is fully TTL com-
patible on input and output lines. The 4804 is
packaged in a convenient 18 pin dual-in-line
package

■ Single I 5V Power Supply

■ 1Kx4 Organization

■ Replaces 4 1024x1 Static RAMs

■ Completely Static— No Clocks or Refresh

■ 18 Pin Package

■ Access/Cycle (JOOnsec max

■ 250 mw Typical Operating Power

■ Common I/O Bus

■ TTL Compatible I/O

■ Three State Outputs

FEATURES

TRUTH TABLE

L
L

R/W

Don't
Care

DI/DO STATUS

High

Data

Deselect

Selected

MODE

Standby

READ

Write

Write
1

WRITE CYCLE-AC CHARACTERISTICS

PARAMETER

SYMBOL

4804
MIN MAX

Write Cycle Time

Twc

600

Address To Write Time

T*/.

100

Write Pulse Width

T.v;

500

Write Recovery Time

T/,"

Data Set Up Time

Tow

350

Data Hold Timo

Tom

Output Disable From Write
or Chip Enable

Totw

150

READ CYCLE-AC CHARACTERISTICS

PARMyYETt*

SYMBOL

4804

MIN MAX

Read Cycle Timo

Tii

600

Access Time

600

Chip Enable to
Output Enable

Tco

200

Data Valid After Address

Tom

150

Previous Data Valid After
Chip De-Select

Tow

$8.95

8/$60.00

16/$l00.00

INTEGRATED TONE RECEIVER

MK5102(N)-5

FEATURES

D Detects all 16 standard DTMF digits

D Requires minimum external parts count for

minimum system cost
D Uses inexpensive 3.579545 MHz crystal for

reference
D Digital counter detection with period averaging

insures minimum false response
G 16 pin package for high system density
n Single supply 5 Volts ♦ 10%
□ Output in either 4-bit binary code or dual 2 bit

row/column code
D Latched outputs

DESCRIPTION

The MK5102 is a monolithic integrated circuit
fabricated using the complementary symmetry MOS
(CMOS) process. Using an inexpensive 3.579545 MHz
television colorburst crystal for reference, the
MK5102 detects and decodes the 8 standard DTMF
frequencies used in telephone dialing. The require-
ment of only a single supply and its construction in a
16pin package make the MK5102 ideal for appli
cations requiring minimum size and external parts
count. DETECTION FREQUENCY

Low Group t

High Group »„

Row t ■ 697 Hz

Column 1 ■ 1209 Hz

Row 2 - 770 Hz

Column 2 ■ 1336 Hz

Row 3 - 852 Hz

Column 3 ■ 1477 Hz

Row 4 ■ 941 Hz

Column 4 ■ 1633 Hz

MK5102N-5 $34.95

Specs 50

600 Ohm to 600 Ohm C.T. transformer $1 .95

Colorburst crystal for above $1 .75

TRITEK

10 AMP REGULATORS
78P05

GENERAL DESCRIPTION- The uA78P05 is a 3-terminal positive
5V hybrid regulator capable of delivering 10 Ampsl This device
is virtually blowout proof and contains all the protection features
inherent in monolithic regulators such as internal short-ciruit
current limiting and thermal -over load protection. The uA78P05
is packaged in a hermetically sealed TO-3 providing 50W at 25°
C case. The hybrid consists of a monolithic control chip driving
a rugged Mesa transistor. The high output current is achieved
through new design technique without sacrificing the regulation
characteristics of the controlling elements. The same process is
employed in the construction of the 10A regulator to provide the
same high reliability obtained in the uA78H05 5A regulator.

COMMON (1)-

OUTPUT (?)

• 10 A OUTPUT CURRENT

• INTERNAL THERMAL-OVERLOAD PROTECTION

• INTERNAL SHORT-CIRCUIT CURRENT LIMIT

• LOW OROP-OUT VOLTAGE 2.2 V AT 10 A

• 50 W POWER DISSIPATION

• PIN-FOR-PIN COMPATIBLE WITH THE kATSHOS.

„A7iH05A AND SH323 CONNECTION DIAGRAMS

• STEEL TO-3 PACKAGE TO-3 PACKAGE

(TOP VIEW)

78P05SC $1 2 .95

Specs °60

MULTI-CHANNEL 8 BIT A/D CONVERTER
Fairchilds' new 6 channel analog-to digital converter has a lot
going for it. Full scale correction capabilities, ratiometric con-
version and wide input dynamic range.

Micro-processor compatible, it combines the multiplexer, decod-
er and sample-and -hold functions with converter to save board
space and eliminate external parts. It provides 8 bit, +5 LSB
conversion in 300 uSec featuring auto-zero and dynamic range
all the way to ground.
UA9708 in 16 pin plastic DIP. $7,951

DIXON

THE THIRD HAND

• This versatile tool has proven its worth through
generations of use by professional craftsmen.

• The Third Hand holds work in any position freeing
both hands to perform other vital functions.

POSITION TWEEZER //
TO LENGTH DESIRED. JF /
TIGHTEN WING SCREW. ^ rf /

CROSSLOCK TWEEZER
Dixon #H-500

• Tweezer exerts 1Vi lb. ten-
sion on blunt ends

J/ 2 w

• Double ball joint allows
positioning of tweezer at
■% any angle

^^ • Heavy Iron base may be
"J held In vise or clamped to

(D ADJUST TfJANGLE DESIRED sft^* 1
ANO TIGHTEN WING SCREW

&P bench

4801 STATIC, TTL IN OUT 4096*1 N-MOS RAM

GENERAL
DESCRIPTION

Part Number 4801
is a 4K semicon-
ductor random
access memory •

organized as 4096 1-bit words. It is fully static and
needs no clock or refresh pulses. It requires a
single I 5 volt power supply and is fully TTL com-
patible on input and output lines. The 4801 is
packaged in a convenient 1 8 pin dual-in-line
package.

■ Single - 5V Power Supply

■ 4Kx1 Organization

■ Replaces 4 1024x1 Static RAMs

■ Completely Static— No Clocks or Refresh
FEATURES ■ 1 8 Pin Package

■ Access/Cycle Times 600 nsec max

■ 250 mw Typical Operating Power

■ Separate Data In and Data Out

■ TTL Compatible I/O

■ Three State Outputs

■ Data Bus Compatible I/O Function

R/W

STATUS

MODE

Don't
Care

High

Deselect

Standby

Don't

Care

Data

Selected

READ

High

Selected

Write

High

Selected

Write

TRUTH TABLE

WRITE CYCLE-AC CHARACTERISTICS

PARAMETER

SYMBOL

4801
MIN MAX

Writo Cycln Time

600

Address To Write Time

TAW

100

Write Pulse Switch

Tai'

500

Write Recovery Time

Twb

Data Set Up Time

T: .-.

350

Data Hold Timo

Tom

Output Disable From Write
or Chip Enable

Totw

150

READ CYCLE-AC CHARACTERISTICS

PARAMETER

SYMBOL

4801
MIN MAX

Read Cycle Time

600

Access Timo

600

Chip Enable to
Output Enable

Tco

200

Data Valid After Address

Tom

1S0

Previous Data Valid After
Chip De-Select

TOH2

$8.95

8/S60.00

16/$100.00

VOLTAGE REGULATORS

7805 06 08- 1 2 1 5 24TO220

78L05A 12-15 4% 100 mA TO-92 Plastic

78H05KC 5V 5A TO-3

78H12KC 12V 5ATO-3

78H15KC 15V 5AT0 3

Lm31 7K 1 .5A Adjustable TO 3

Lm3 1 7T 1 . 5 A Adjustable TO 220

Lm3 1 7MP . 5A Adjustable TO-202

TL430C Adjustable ZenerThink About It

TL497C Switching Reg. & Inductor

RCA CA 3085 100 mA Adjustable

Signetics 2504TA I024 bit S.R. memory (1404A).

MCM 657 1P Character Generator

MCM6571AP Character Generator

MC14409P Telephone Rotary Pulser

MC14419P Touch Pad Converter for 14409

MC 1441 IP Baud Rate Generator

MC14412VP CMOS Modem Chip

MM57109N Number Cruncher Micro

74C915 7 Segment to BCD Converter

74C922 16 Key Keyboard Encoder

74C923 20 key Keyboard Encoder

74C925 4 Decade Counter w/latches

74C926 4 Decade Counter w/carry

74C935 1 3% Digit DVM CMOS Chip

95c 5/$4.50

50<
8.45 I
9.15
9.15
4.99
3.99
13.95
1.50
9.50
.60

. .50

9.95

10.98

4.25

11.98

16.95

18.95

2.99

6.35

645

12.00

16.98

• FREES HANDS

Dixon Third Hand... $7. 95

Jumper Kits for .025 Square Posts. .
All material for making jumpers for
quick circuit changes and proto-
typing. Use for breadboard ing,
trouble shooting, field modifications.
Fits standard IC socket wire/wrap
ill posts. Excellent wiping action on
. \-\j g°ld plated box contacts.
I -I Kit contain 10 box contacts, heat

shrinkable sleeving, and 5 feet of wire plus instruction
sheet.
JCK-5I0I (5 double jumpers) $2. 75, 4 kits/SIO.OO

DEALER PRICING AVAILABLE UPON REQUEST

W Till TEH

7808 North 27th Avenue
Phoenix, Arizona 85021
(602) 9959352

• Please give street address <or UPS snipping when possible

• CO.O. NO parcel pott COD.

UPS C.O.D. Add 85« to order.

• Any correspondence not connected with your order.

please use separate sheet and include SASE for reply.

• Orders less than $10 (SIS foreign) please add *l
handling.

• Prices are subject to change without notice.

• Any refunds win be by check, not credit vouchers.

• Terms. Check, money order, credit card. Net 30 days to
rated firms, schools and government agencies.

if we should be temporarily out of stock on tn item, it
will be placed on back order, if we cannot ship in 30
days, you will be notified of the expected shipping date
and furnished with a postage paid card with which to
cancel your order if desired.

surface shipping only in USA, Canada and

We pay

Mexico.

For premium shipping (first class, special handling, etc.)

add extra. Excell will be refunded.

Foreign orders (except Canada and Mexico) estimate and
add shipping. Excess will be refunded

Charge card telephone orders I $20 mm } will be
accepted 9530 PM. except weekends.
Telephone 995 9352. No collect calls please

131

DIODES/ZENERS

SOCKETS/BRIDGES

TRANSISTORS, LEDS, etc.

1N914

100v

10mA .05

8-pin pcb .20 ww .35

2N2222

NPN (2N2222 Plastic. 10)

.15

1 N4005
1 N4007

600v
1000v

1A .08
1A .15

14-pin pcb .20 ww .40
16-pin pcb .20 ww .40

2N2907
2N3906
2N3904

PNP

PNP (Plastic - Unmarked)

NPN (Plastic - Unmarked)

.15
.10
.10

1N4148

75v

10r

18-pin pcb .25 ww .75

2N3054

NPN

.35

1N4733

5.1v

1 \N

' Zener .25

22-pin pcb .35 ww .95

2N3055

NPN 15A 60v

.50

1N753A
1N758A

6.2v
10v

500 mW Zener .25

.25

24-pin pcb .35 ww .95
28-pin pcb .45 ww 1.25

T1P125
LED Green,
D.L.747

PNP Darlington
Red, Clear, Yellow
7 seg 5/8" High com-anode

.95

.15

1.95

1N759A

12v

.25

40-pin pcb .50 ww 1.25

MAN72

7 seg com-anode (Red)

1.25

1N5243
1N5244B

13v
14v

.25
" 25

Molex pins .01 To-3 Sockets .25

MAN3610
MAN82A

7 seg com-anode (Orange)
7 seg com-anode (Yellow)

1.25
1.25

> » %^ ^^m W V ft«^

1N5245B

15v

.25

2 Amp Bridge 100-prv .95
25 Amp Bridge 200-prv 1 .95

MAN74A
FND359

7 seg corn-cathode (Red)
7 seg com-cathode (Red)

1.50
1.25

CMOS

- T T L -

4000

.15

740C

» .10

7473 .25

74176 .85

74H72

.35

74S133

.40

4001

.15

7401

.15

7474 .30

74180 .55

74H101

.75

74S140

.55

4002

.20

7402

.15

7475 .35

74181 2.25

74H103

.55

74S151

.30

4004

3.95

7403

I .15

7476 .40

74182 .75

74H106

.95

74S153

.35

4006

.95

7404

.10

7480 .55

74190 1.25

74S157

.75

4007

.20

740E

i .25

7481 .75

74191 .95

74 LOO

.25

74S158

.30

4008

.75

7406

.25

7483 .75

74192 .75

74L02

.20

74S194

1.05

4009

.35

7407

.55

7485 .55

74193 .85

74L03

.25

74S257(8123)

1.05

4010

.35

740£

I .15

7486 .25

74194 .95

74L04

.30

4011

.20

740S

l .15

7489 1.05

74195 .95

74L10

.20

74LS00

.20

4012

.20

741 C

I .15

7490 .45

74196 .95

74L20

.35

74LS01

.20

4013

.40

7411

.25

7491 .70

74197 .95

74L30

.45

74LS02

.20

4014

.75

7412

! .25

7492 .45

74198 1.45

74L47

1.95

74LS04

.20

4015

.75

7413

I .25

7493 .35

74221 1.00

74L51

.45

74LS05

.25

4016

.35

7414

.75

7494 .75

74367 .75

74L55

.65

74LS08

.25

4017

.75

7416

i .25

7495 .60

74L72

.45

74LS09

.25

4018

.75

7417

.40

7496 .80

751 08A .35

74L73

.40

74LS10

.25

4019

.35

742C

I .15

74100 1.15

75491 .50

74L74

.45

74LS11

.25

4020

.85

7426

.25

74107 .25

75492 .50

74L75

.55

74LS20

.20

4021

.75

7427

.25

74121 .35

74L93

.55

74LS21

.25

4022

.75

743C

l .15

74122 .55

74L123

.85

74LS22

.25

4023

.20

7432

.20

74123 .35

74H00 .15

74LS32

.25

4024

.75

7437

.20

74125 .45

74H01 -20

74S00

.35

74LS37

.25

4025

.20

7438

.20

74126 .35

74H04 .20

74S02

.35

74LS38

.35

4026

1.95

7440

.20

74132 -75

74H05 .20

74S03

.25

74LS40

.30

4027

.35

7441

1.15

74141 .90

74H08 .35

74S04

.25

74L.S42

.65

4028

.75

7442

.45

74150 .85

74H10 .35

74S05

.35

74LS51

.35

4030

.35

7443

.45

74151 .65

74H11 .25

74S08

.35

74LS74

.35

4033

1.50

7444

.45

74153 .75

74H15 .45

74S10

.35

74LS86

.35

4034

2.45

7445

.65

74154 .95

74H20 .25

74S11

.35

74LS90

.55

4035

.75

7446

» .70

74156 .70

74H21 .25

74S20

.25

74LS93

.55

4040

.75

7447

.70

74157 .65

74H22 .40

74S40

.20

74LS107

.40

4041

.69

7448

.50

74161 .55

74H30 .20

74S50

.20

74LS123

1.00

4042

.65

7450

I .25

74163 .85

74H40 .25

74S51

.25

74LS151

.75

4043

.50

7451

.25

74164 .60

74H50 .25

74S64

.15

74LS153

.75

4044

.65

7453

! .20

74165 1.10

74H51 .25

74S74

.35

74LS157

.75

4046

1.25

7454

.25

74166 1.25

74H52 .15

74S112

.60

74LS164

1.00

4049

.45

7460

I .40

74175 .80

74H53J .25

74S114

.65

74LS193

.95

4050

.45

7470

i .45

74H55 .20

74LS367

.75

4066
4069/74 C04

.55
.25

7472

.40

74LS368

.65

4071

.25

MCT2 .95 LIIMEARS, REGULATORS, etc.

4081

.30

8038 3.95

LM320T5 1.65

LM340K15

1.25

LM723

.40

4082

.30

LM201 .75

LM320T12 1.65

LM340K18

1.25

LM725N

2.50

MC 14409 14.50

LM301 .45

LM320T15 1.65

LM340K24

1.25

LM739

1.50

MC 14419

4.85

LM308 (Mini) .95

LM324N 1.25

78L05

.75

LM741(8-14).25

4511

.95

LM309H .65

LM339 .75

78L12

.75

LM747

1.10

74C1 51

1.90

LM309K (340K-5>85
LM310 .85
LM311D(Mini) .75

7805 (340T5) .95
LM340T12 .95
LM340T15 .95

78L15
78M05
LM373

.75

2.95

LM1307
LM1458
LM3900

1.25
.65
.50

9000 SERIES

9301 .85

95H03

1.10

LM318<Mini) 1.75

LM340T18 .95

LM380(814pin).95

LM75451

.65

9309 .35

9601

.20

LM320K5(7905)1.65

LM340T24 .95

LM709(8,14pin).25

NE555

.35

9322 .65

9602

.45

LM320K12 1.65

LM340K12 1.25

LM711

.45

NE556
NE565

IV 1 T~ CT&&

.85

.95

1.25

.95

MICRO'S, RAMS. C

PITS,

E-PRC

74S188 3.00
1702A 4.50

)MS

8214
8224

8.95
3.25

INTEGRATED CIRCUITS UNLIMITI

NE566
NE567

MM5314 3.00

8228

6.00

7889 Clairemont Mesa Boulevard, San Diego, California 92111

MM5316 3.50
2102-1 1.45

8251
8255

8.50
8.50

(714) 278-4394 (Calif. Res.)

SPECIAL
DISCOUNTS

2102L-1 1.75

8T13

1.50

All orders shipped prepaid No minimum

Total Order

Deduct

2114 9.50
TR1602B 3.95

8T23
8T24

1.50
2.00

Open accounts invited COD orders accepted $35- $99

10%

TMS4044- 9.95

8T97

1.00

Discounts available at OEM Quantities California Residents add 6% Sales Tax V 00 ' ? 300 _

15%

2107E

1-4 4.95

All IC's Prime/Guaranteed. All orders shipped same day received.

$301 $1000

20%

8080 8.95
|8212 2.95

2708
Z80P

9.50
10 8.50

24 Hour Toll Free Phone 1-800-854-221 1 American Express / BankAmericard / Visa / Master Charge

SALE S-100 BUS EDGE CONNECTORS SALE

SALE

ILM3A 3dig 1%DC $134.00

LM3.5A 3% dig .5% DC ... $ 158.50

LM40A 4 dig .1% DC $209.00

|LM4A 4 dig .03% DC $250.00

Rechargeable batteries and charger in-
cluded

Measures DC Volts, AC Volts, Ohms and

Current

Automatic polarity, decimal and overload

indication

Rechargeable batteries and charger

Measures DC Volts, AC Volts, Ohms and

Current
| • Automatic polarity, decimal and overload

indication

No zero adjustment and no full-scale ohma

adjust

Battery-operated — NiCad batteries; also AC

line operation.

Large LED display for easy reading without

interpolation

Size: 1.9"Hx2.7"Wx4"D

Parts & labor guaranteed 1 yaar

Tilt stand option * *•*■

Laathercasa * 200a

Purchase any of the LM series

Meters and buy the LEA J HER CASE

for 10

•

■ *

•*0<M*aM'* " M

$318.

*' : » ■' J '

MS 75 MINISCOPE

With flecharoeabre Berfer/es ft Ctl»rg»r Unit

PROBE 1C

PROBE K with the

purchase o< SCOPE

land the MENTION of

this MAGAZINE

8803

MOTHER
BOARD FOR
SIM BUS
MICRO-
COMPUTERS

• Kit includes 1?
tantalum capaci
Iocs lor +5 .♦ 12.
— 1? busts and in su
HIM mounting spacers

• Wiring sifle shown Com
ponent side ban apoiy
glass win while makings tor
component locations

• GtO epoiy glass board with 2 ounce,
copper solder Dialed and 038 diame
ttr notes tor leads

• Solder mask with solder windows on
etched circuits to avoid accidental short
circuits

• Mounts 1 1 receptacles with 100 contacts (2
rows) on 125 centers with ?W row spacing
Vector part number D6II ? or mounts 10 recap
tacles plus interconnections to smaller mother board
lor enpansion

• includes etched circuits and instructions tor option ol
active pull up. or floating terminations

• Large buses +■>¥ ano GN0O0 AMPSl ♦ '?Vor 16V (7
AMPS) Current ratings are per Mil STO 275 with 10*C
rise

• Fits in vector pax enclosures

• Fits in IMSAI 8060 microcomputer as eipander board

•15 megahertz bandwidth.

• External and internal trigger.

• Time base — 1 microsec to 5 Sec/div • 21
settings .±-3%.

• Battery or line operation.

• Automatic & line sync modes

• Power consumption < 15 watts.

• Vortical Gain — 01 to SO V/div 12 tattings t 3%

• Viewing area 1 1 ' x 1 35

• Case ana 2 7"H « 6 4 "W a 7 5"D. 3 pounds

• Pint A Labor guaranteed ' year

• 10 to 1 10 meg probe

• Leather carrying caee a *J5. .

• MS-215 Dual Trace Version of MS-15 $435.

$27.

*, S-100 BUS EDGE CONNECTORS ^

S100 WWG 50 lOOCont 125ctrs
3 LEVEL WIRE WRAP 025 sq posts
on 250 spaced rows GOLO plated

14 5 9 10 24

• 4 00 »3 75 »3 50

RG81G 50 100 Coot 125ctrs DIP
SOLOERTAILon 1 40 spaced rows tor
ALTAIR motherboards GOLO plated

• 600

S100 STG 50 100 Com 125ctrs
DIP SOLDER TAIL on 250 spaced
rows tor VECTOR and MASI

motherboards GOLD plated
14 6 9 10 24

S4 00 S3 75 S3 50

R681 3 50 100 Cont 125 ctrs
PIERCED SOLDER EYELET tails
GOLD
• 7 36

Other Popular Edge Connectors

R644 G 22 44 Cont 156 ctrs
PIERCED SOLDER EYELES tails
GOLD plated

14 59 10 24

• 3 00 *2 76 «2 60

R644 3 22 44 Cont
WRAP tails GOLD
•4 71

156 ctrs WIRE

ATTN OEM'S and Dealers many other connectors available call or quotation

1-24

8 pin # 41

14 pin* 39

16 pin* 43

18 pin 63

20 pin 80

22 pin* 90

24 pin
28 pin
40 pin

90
1 10
1.50

25-49
38
38
42

58
75
85

84
1.00
1 40

50-99
35
36

54
70
80

1.30

100-249
31
32
35

47
63
70

1 20

250 999
27
29
32

42
58

1.04

1K-5K
23
27
30

36
53
57

58
71
89

Sockets purchased in multiples of 50 per type
may be combined for best price.

All sockets are GOLD 3 level closed entry * End and side
stacable. 2 level, Solder Tail, Low Profile, Tin Sockets and
Dip Plugs available. CALL FOR QUOTATION

f em 9 i

Price:
$29.50

1/16 VeOOl BOARD

.042 dia holes on
0.1 spacing for IC's

PRICE

PART NO SIZE 1-9 10-19

64P44XXXP 4 5x6 5" $1.49 13 4
169P44XXXP 45x17" S3 51 3 16

Epoxy Glass

64P44

45x65"

$1.70

1 53

84P44

45x85"

$2 10

1.89

1 69P44

4 5x17"

$430

387

169P84

8 5x17"

$765

689

Plugboards

8800V

Universal Microcomputer/processor
plugboard, use with S-100 bus Com-
plete with heat sink & hardware b 3 x
10 x 1/16

1-4 5-9 10-24

$1995 $1795 $1596

8801-1

Same as 8800V except plain, less power
buses & heat sink
1-4 5-9 10-24

J14JJ5 — ^ — ^jnjSJj.

3682 9.6" x 4.5"
$10.97

3682-2 6.5" x 4.5"
$9.81

Hi-Density Dual-ln-Line
Plugboard for Wire Wrap
with Power & Grd. Bus
Epoxy Glass 1/16" 44
pin con. spaced .156

3677 9 6" x 4.5'

$10.90

3677-2 6.5" x 4.5"

$9.74

Gen. Purpose D.I. P.
Boards with Bus Pattern
tor Solder or Wire Wrap.
Epoxy Glass 1/16" 44
pin con. spaced .156

3662 6.5" x 4.5"

$7.65

3662-2 9.6" x 4.5"

$11.45

P pattern plugboards tor
IC's Epoxy Glass 1/16"
44 pin con spaced 156

3690-12
CARD EXTENDER

Card Extender has 100
contacts-50 per side on 125
centers-Attached connector-is
compatible with S-100 Bus

Systems $25.00

3690 6 5 22/44 pin .158
ctrs. Extenders $ 1 2 .00

Wraps msulalad wire on 025" square posts
FOUR TIMES FASTER

trtan regular "tarn** wap oo«t tools ,

P180

with two

100' spools

ot 28 ga

wire

$24.50

Urn® ^

NO PRE STRIPPING

NO PRE -CUTTING*

SPOOL FED WIRE'

'The spooled win passes through the tool past a slitting edge

next to the wrap post A narrow longitudinal cut is made in the

insulation where it presses the square post

corn* NW M'M cooper 4 moantad by "W SKarp allot
|" lurns- It contacts

I****** a v* **wt *<aaaM a«i *m
«*w wi «■*«*' ».' * ** *•

P180-4T

Includes

charger, wire

$75.00

Qany-cham runt
rtaiia tit and easy to use

Manual or power operetnn

SLIT N WRAP . 2 " PKk ^.

WIRE

NO 28 GAGE INSULATED

WIRE. 100' SPOOLS

W?8 ? » Pkg 3 GrMn W?8 ? C Pkg 3 Cltar
w?8 ? 8 Pkg 3 DM W?8 ? Bhg 3 Blue

2708

8K 450 ns

EPROM

FACTORY PRIME

$ 9.00 EA.

25 + Call For
Price

LIQUID CRYSTAL DIGITAL
CLOCK-CALENDAR

a For Auto, Home, Office
a Small in size (2x2 HxVfc)
a Push button for seconds release for date.

• Clocks mount anywhere with either 3M double
sided tap* or VELCRO. included

• 2 MODELS AVAILABLE

LCD- 101. portable model runs on sett -contained
batteries tor better than a yaar
LCD 102. runs on 12 Volt system and Is beck
lighted I

• LCD 101 or LCD 102 # O M AC

$2.00

your choice

Cteev doth stand tor

MICRO-KLIP

for .042 dia holes
(all boards on this page)
T42-1 pkg 100 $ 1.50
T42-1 pkg

1000 $11 00

P-149 hand installing

tool $ 2.03

$0- 7

WRAP POST

for .042 dia holes
(all boards on this page)
T-44pkg 100 S 2. 28
T-44 pkg

1000 $14 00

A-13 hand installing

tool $ 2.80

♦eeeeae.eee-.eeeeee

LED ALARM CLOCK

12 hr LED Alarm Clock uses 3'/z
digit 8" LED Display with AM/PM
indicators and colons Direct drive
PIN to PIN interlace with S1998A
I.C. Just add switches. AC Supply.
Alarm. Display and I C only

$7.95 or 2/S15.00

$4495

SPECIAL

Perfectly balanced, fluorescent
lighting with precision magnifier
lens For prof'l. techn : & hobbist
Has die cast protective shade, mst start
3 diopter lens 42 " reach

-M, : •• P.IH

SC5
With
Rechargeable
Batteries •
Charger
Unit £ 98

14 & 16 PIN
iV^GOLD 3 LEVEL
( U eH>\WIRE WRAP
SOCKETS

14 - G3 100 for
$30.00
16-G3 100 for
$30.00
50 of each for $32.00

Sockets are End & Side stackable,
closed entry

FM-7
With

Rechargeable
Batteries ft
Charger

unit $215

Features include • By using the new NiS SC 5 Prescaier the range of
the FM-7 Frequency Meter, which is 10 Hi to 60 MHz. may be extended
to 51? MHz (the upper VHF & UHF frequency bands) • The FM-7 uti-
lizes an LED readout, providing 7 digit resolution • The FM-7 can be
calibrated to an accuracy ol 00001 % • The SC S is accurate to one
part per million • Each unit has 30 millivolts sensitivity, is battery
powered and has a charger unit included • Dimensions of each are 1 9
H « 2 7' W x 3 9 D • The units may be obtained separately or as a

F requency Duo • Pans ft Labor guaranteed 1 year
Tilt stand option 1 3 50

Leather case $20.00

PRIORITY

Price Breakthrough! $-1750

«••••»»••■•"'•■■

I2:HB

mmmrTtrrrnmi #

MA1003
CAR CLOCK

Bright Green Fluorescent Display Crys-
tal Time Base Assembled, just add
switches and 12VDC.

SPECIAL

14CS2100for»14 M
16CS2 100forM6 , °

14 pin CS2 10 for *2"
16 pin CS2

8 lor *T*

These low cost DIP sockets will accept
both standard width plugs and chips.
For use with chips, the sockets otter a iow
profile height of only .125" above the board.
These sockets are end stackable.

ELECTRONICS

P21

Sepul

Send for our latest brochure

Terms VISA. MC, BAC, check, Money Order. COD , U.S. Funds Only CA residents add 6% sales tax. Mini-
mum order $10 00 Orders less than $75 00 include 10% shipping and handling; excess refunded. Just in case
. . . please include your phone no. " Sorry, no over the counter series" GOO ° ™ ,u »"»«»*■" " 7t

phone orders welcome (213) 893-8202

OEM and Institutional inquiries invited

24 PIN DIP PLUGS
WITH COVERS

3/ $1.00
40/ $10.00

SALE S-100 BUS EDGE CONNECTORS SALE

ELPAC

POWER

SUPPLIES

Completely Assembled
SPECIFICATIONS:

105-125 710-250 Vac. 47-440 Hz input:

Line Regulation ±0.1%

Load Regulation ±0.1%no-load to rated-load

Output Ripple and Noise ±0.1%p-p,dc to 10 MHz
Input/Output Isolation 100 megohm dc. 900 Vac
Short Circuit Current 35% rated current
PART NO. RATINGS PRICE

WATTS VOLTS

SOLV15-5* 15 5

S0LV15-12* 18 12

S0LV30-5 30 5

SOLV30-12 48 12

0VP1 over voltage protection for SOLV30-5

•SOLV15-5. 12 includes OVP installed

AMPS

1.5
6
4
12

$39 95

39.95

59.95

9.95

SUP R' MOD II

UHF Channel 33 TV Interface Unit Kit

*Wide Band B/W or Color System

* Converts TV to Video Display for
home computers, CCTV camera,
Apple II, works with Cromeco Daz-
zler, SOL-20, IRS-80, Challenger,
etc.

* MOD II is pretuned to Channel 33
(UHF)

* Includes coaxial cable and antenna
transformer.

MOD II

$29.95 Kit

-^'CRYSTALS «r-

PART NO.

CY1A

CY1 84

CY2A

CY201

CY2 50

CY327

CY3 57

CY3A

CY4 91

CY7A

CY5 18

CY6 14

CY6 40

CY6.55

CY12A

CY14A

CY19A

CY1843

CY22A

CY30A

THESE FREQUENCIES ONLY
FREQUENCY CASE

PRICE

1
1

2
2
2
3
3
4
4

000MHz
8432MHz
000MHz
010MHz
500MHz
2768MHz
579545MHz
000MHz
916MHz
5.000MHz

5 185MHz

6 144MHz
6 400MHz
65536MHz
10000MHz
14 31818MHz
18 000MHz
18432MHz
20 000MHz
32 000MHz

HC33
HC33
HC33
HC33
HC33
HC33
HC33
HC18
HC18
HC18
HC18
HC18
HC18
HC18
HC18
HC18
HC18
HC18
HC18
HC18

Custom Cables & Jumpers

95
95
95
95
95
95
95
95
95
95
95
95
95
95
95
95
95
95
95
95

Part No.

DB25P-4-P
DB25P-4-S
DB25S-4-S

DJ14-1

DJ16-1

DJ24-1

DJ14-1-14

DJ16-1-16

DJ24-M6

DB 25 Series Cables
Cable Length Connectors Price

4 Ft. 2-DP25P $15.95 ea

4 Ft. 1-DP25P/1-25S $16.95 ea.

4 ft 2-DP25S $17.95 ea.

Dipped Jumpers Plugs

1ft. 1-14 Pin $1.59 ea.

1ft. 1-16 Pin 1.79 ea.

1ft. 1-24 Pin 2.79 ea.

1 ft. 2-14 Pin 2.79 ea.

1ft. 2-16 Pin 3.19 ea

1 ft. 2-24 Pin 4.95 ea.

For Custom Cables & Jumpers. See JAMECO 1979 Catalog for Pricing

• 4 • • *

PHENOLIC

EPOXY
GLASS

EPOXY GLASS
COPPER CLAD

1/16 VECTOR BOARD

1 Hole Spacing P Pattern Price

Part No L W 1-0 10 up

64P44 062XXXP 4 50 6 50 1 72 1 54

169P44 062XXXP 4 50 17 00 3 69 3 32

64P44 062WE 4 50 6 50 2 07 1 86

84P44 062WE 450 850 256 2 31

169P44 062WE 4 50 17 00 5 04 4 53

169P84 062WE 8 50 17 00 9 23 8 26

169P44 062WEC1 4 50 17 00 6 80 6 12

i- CONNECTORS

25 Pin-D Subminiature

DB25P(as pictured) PLUG $2 95

DB25S SOCKET 3.50

DB51 226-1 Cable Cover for DB25 P or S 1.75

MOLEX CONNECTOR PINS

ffli wi Ma Jgiiiiii i

Pre-packaged in strips

M-530-1

$1.95/100 pins
(minimum order)

$16.00/1000 pins

INSTRUMENT/
LOCK CASE

llnjectton molded unit.
[Complete with red bezel
UVx 4" x 1-9/16".

$3.49

CDP 1802

P8085

8080A

8212

8214

8216

8224

8228

8251

8253

8255

8257

1101

1103

2101(8101)

2102

2107/5280

2111(8111)

2112

2114

2114L

2114-3

2114L-3

7489

6599

21L02

74S200

93471

MICROPROCESSOR COMPONENTS

WM5262

CPU $19 95

CPU 19.95

CPU 9.95

8-Bit Input/Output 3.25

Priority Interrupt Control 5.95

Bi-Directional Bus Driver 3.49

Clock Generator/Driver 3.95
System Controller/BusOriver 5 95

Prog. Comm. Interface 7 95

Prog Interval Timer 14.95

Prog. Periph Interface 9.95

Prog DMA Control 19.95

RAM'S

256 x 1 Static $ 1 49

1024 x 1 Dynamic 99

256 x 4 Static 3 95

1024 x 1 Static 1 75

4096 x 1 Dynamic 4 95

256 x 4 Static 3 95

256 x 4 Static 4 95

1024 x 4 Static 450ns 9 95
1024 x 4 Static 450ns Low Power 10 95

1024 x 4 Static 300ns 10 95
1024 x 4 Static 300ns Low Power 1 1 95

16x4 Static 175

16 x 4 Static 3 49

1024 x 1 Static 1 95

256 x 1 Static 4 95

256 x 1 Static 2.95

CPU
1)CPU
MPU
MPU
126 x 8 Static Ram

Z80(780C)

Z80A( 708-1

2650

MC6800

MC6810API

MC6821 Periph. Interface Adapter(6820)7 49

MC6830L8

MC6850

MC6852

MC6880

$19.95
24.95
26 50
14.95
595

MC6802

1702A

5203

82S23

82S115

82S123

74S287

TMS2532

2708

2716 T I

1024x8BttROM(68A30)
Asychronous Comm Adapter
Syn Serial Data Adapter
(MC8T26) Quad Tri State
Bus Trans
MPU w/Clock & Ram

1495
795
995

2048 x 1
2048 x 1
32x8
4096 x 1
32x6
1024 x 1
32K
8K
16K

2716 Intel (2516 T I) 16K
6301-1 1024x1

6330-1 256 x 1

PROMS

Famous

Open C

Bipolar

Tristate

Static

EPROM

EPFtOM

EPROM

Tn-State Bipolar

Open C Bipolar

MK4027 (UPD414) 4K

MK4116(UPD416) 16K

TMS4044-45NL 4K

2513(2140)
2513(3021)
2516

MMS230N

2K x 1 Dynamic '

170B

1802M

Z80M

2650M

DYNAMIC 16 PIN 4 95

DYNAMIC 16 PIN 14 95

STATIC 1495
ROM'S

Character Generator (upper case) $ 9 95

Character Generator (lower case) 9 95

Character Generator 10 95

2048 Bit Read Only Memory 1 95

USER MANUALS

CDP 1802 Manual i 7 50

Z80 Manual 7 50

2650 Manual 5 00

MM5016H

2504T

2518

2522

2524

2525

2527

2528

2529

2532

2533

3341

74LS670

AY-5-1013

SHIFT REGISTERS

500/512 Bit Dynamic
1024 Dynamic
Hex 32 Bit Static
Dual 132 Bit Static
512 Dynamic
1024 Dynamic
Dual 256 Bit Static
Dual 250 Static
Dual 240 Bit Static
Quad 80 Bit Static
1024 Static
Fifo

4x4 Register
UARTS

30K BAUD

2.25
24 95

$5 95

14 95

395

1995

395

2 95

99 95

1095

29 95

49 95

349

295

89
395
495
295

99
295
295
400
400
295
295
6 95
1 95

S 595

TELEPHONE

KEYBOARD CHIPS
AY 5-9100 $14 95
AY -5-9200
AY-5-9500
AY-5-2376
HD0165
74C922

SPECIAL REQUESTED ITEMS

ICM CHIPS

14 95
495

14 95
7 95
9 95

ICM7045
ICM7205
ICM7207
ICM7208
ICM7209

$24 95

19 95

7 50

19 95

6 95

NMOS READ ONLY
MEMORIES

MCM6571 $13 50
MCM6574 13 50
MCM6575 13 50

MISCELLANEOUS

TV GAME CHIP SET

AY-3-8500-1 Chip and

2 010 MH2 Crystal

S7.95[

11C90 $1995

MC3061P 1195

MC1408L7 495

MC1408L8 5 75

LD110/111
MC401 6(744 16)

4N33

MK40240 $17 50
DS0026CH 3 75
TIL308 10 20

95H90 11 95

$25 00/set

750

395

The Sinclair PDM35.

A personal digital

multimeter for only $59 M

A digital multimeter used to mean jn
expensive, bulky piece of equipment.

The Sinclair PDM35 changes that Its
got all the functions and teaturesyou want
in a digital multimeter, yet they're neatly
packaged in a rugged but light pockeisi/e
case, ready to go anywhere.

Now everyone can afford to own • digital

multimeter

The Sinclair PDM.'S is supplied com-
pletcly assembled with test leads and prods,
protective wallet and Operator's Manual

The Sinclair PDM.15 is tailor-made loi
anyone who needs to make rapid measure-
ments Development engineers, field service
engineers, lab technicians, computer spe
cialists. radio and electronic hobby ists will
find it ideal

PART NO

PDM35

PDM-AC

PDM-DP

DESCRIPTION

Digital Multimeter

U7volt AC Adapter

Deluxe padded carrying case

PRICE

$59.95
6.95
6.95

Taxnnlcal •p*crftcaft*n
DC Volu (4 ran**.)

Range I mV to 1000 V

Accuracy of reading I OH ± I count

Sole 10 M 1 1 input impedance

AC Vo|u<««Hi-SkHi>

Range IV to MOV

AatHKI ol reading 1 OH i 2 counts

DC Current (• range t )

Range I r»A to 200 mA

Accuracv of reading I OH i I count

Voir Max resolution 0.1 nA

Reiraiance (S rang**)

Range In to 20 Mil

Accuracv of reading 1 5H ± I count

Also provides S lunction-teM ranges

Dimemiona: 6 in i J in i I i in

Weight: 6 ; ot

Power supply: 9 V batten or

Sinclair AC adapter (Balury not mci

Sockets: Standard 4 mm for
resilient plugs

Optional AC adapter lor 117 \
60 11/ power De-lune padded
earning waller

'*§€ PRECISION

Model 2800

$99.95

Comes with test

leads operating manual

and spare fuse

3V»-Dlgit Portable OMM

• Overload Protected

• 3 nigh LED Display

• Battery or AC operation

• Auto Zeroing

• 1mv 1Va 1 ohm resolution

• Overange reading

• 10 meg input impendence

• DC Accuracy 1°o typical
Ranges: DC Voltage - -1000V
AC Voltage 1000V

freq Response 50-400 HZ
DC/AC Current 100mA
Resistance 0-10 meg ohm
Sue 6 4x44 x 2

Accessories:
AC Adapter BC 28 $9.00
Rechargeable

Batteries BP-26 20.00
Carrying Cast LC-28 7.50

100 MHz 8-Digit Counter

• 20 Hz-100 MHz Range • Four power souces. i e

• 6" LED Display batteries. 1 10 or 220V with

• Crystal -controlled timebase charger 12V with auto

• Fully Automatic lighter adapter and external

• Portable — completely 7 2-10V power supply
self-contained MAX-100

Sim — 1 75" x 7 3T

x5 6T

$134.95

ACCESSORIES FOR MAX 100:

Mobili dtaraer Eliminator

use power from car battery Model 100 — CLA $3 95

Charger /Eliminator

use 110 VAC Model 100 - CAI $9 95

63-Key Unencoded

KEYBOARDS

Hexadecimal Key Pad
Unencoded

This is a 63 -key, terminal Keyboard newly
manufactured by a large computer manufac-
turer. It is unencoded with SPST keys, unat-
tached to any kind of PC board. A very solid
molded plastic 13x4" base suits most applica-
tion, in STOCK $29.95/each

19-key pad includes 1-10 keys,
ABC0EF and 2 optional keys and a
shift key. $10.95/each

$5.00 Minimum Order - U.S. Funds Only
California Residents - Add 6% Sales Tax

Spec Sheets - 25*

1979 A Catalog Available— Send 41 c stamp

^*%*<*

ameco

ELECTRONICS

■ di.iuoit oT JAMES ELECTRONICS or CalrfornK

PHONE

ORDERS

WELCOME

(415) 592-8097

MAIL ORDER ELECTRONICS - WORLDWIDE
1021 HOWARD AVENUE, SAN CARLOS. CA 94070

Advertised Prices Good Thru November

The Incredible
Penny whistle 103'

$139.95

Kit Only

The Pennywhittle 103 is capable of recording data to and from audio tape without

critical speed requirements for the recorder and it is able to communicate directly with

another modern and terminal for telephone "hamming" and communications In

addition, it is free of critical adjustments and is built with non precision readily available

parts

Oats Transmission Method Frequency Shift Keying tull-duplex (half -duple*

selectable)

Mmmum Dili Rate 300 Baud

Data Format Asynchronous Serial (return to mark level required

between each character)
Receive Channel Frequencies . . .2025 Hz for space 2225 Hi for mark
Transmit Channel Frequencies . Switch selectable Low (normal) 1070 space.

1270 mark. High 025 space. 2225 mark

Receive Sensitivity 46 dbm accoustically coupled

Transmit Level 15 dbm nominal Adjustable from 6 dbm

to 20 dbm
Receive Frequency Tolerance . . .Frequency reference automatically ad|usts to

allow for operation between 1800 Hz and 2400 Hz
Digital Data Interlace EIA RS-232C or 20 mA current loop (receiver is

optoisolated and non -polar)

Power Requirements 120 VAC. single phase. 10 Watts

Physical All components mount on a single 5" by 9"

printed circuit board All components included
Requires a VOM. Audio Oscillator Frequency Counter and/or Oscilloscope to align

3*> the 3 rd Hand

$9.95 each

'Leaves two hands free for
working

* Clamps on edge of bench, table
or work bench

* Position board on angle or flat
position for soldering or clipping

■ Sturdy, aluminum construction
for hobbyist, manufacturer or
school rooms

TRS-80 16k

Conversion Kit

Expand your 4K TRS-80 System to 16K. Kit
comes complete with:

* 8 each UPD416 (16K Dynamic Rams)

* Documentation for conversion

TRS-16K $115.00

Special Offer - Order both your TRS-16K and the
SupR' MOO II Interface kit together (retail value
$144 95) for only $139.95

3 1/2 DIGIT DPM KIT

• New Bipolar Unit • Auto Polarity

• Auto Zeroing • Low Power

• .5" LED • Single IC Unit

Model KB500 DPM Kit $49.00

Model KB503 5V Power Kit $17.50

JE701 ClOCk Kit -W^OO Height Common

|t> Uses MM5314 Clock Chip
Push Button Switches for setting
Hours, Minutes & Hold.
I* Easily Viewable to 20 Feet
I • Simulated Walnut Case

• 115 VAC Operation

• 12 or 24 Hour Format

• Includes all Components & Case

6WX3 WX1K"

$19 95pef Kit

JE803 PROBE

The Logic Probe is a unit which is lor trie most part
mdespensible m trouble snooting logic tamilies
TTL DTI RTl CMOS It derives trie power *
needs to operate directly oft ol the circuit undei
lest drawing a scant 10 rnA man it uses a MAN i
readout to indicate any ol the loiiowmg states Dy
these symbols (Mi 1 ilOWi oiPUlSEl P The
Probe can detect high frequency pulses to 45 MH;
It can i be used at M0S levels or circuit damage
will result

$9.95 Per Kit

printed circuit board

T 2 L 5V 0.5A Supply

This is standard TTL power supply using the well
known LM309K regulator IC to provide a solid 0.5
AMP of current at 5 volts We try to make things easy
for you by providing everything you need in one
package including the hardware for only

JE225 $9.95 Per Kit

CM'OMl. inCKW OOWMIIKW

PROTO BOARD 6

$15.95

(6 long X 4" wide)

PROTO BOARDS

PB100 - 4 5 x6" $ 19.95

PB101 - 5.8 ' x4.5" 22.95

PB102 -7" x4.5" 26.95

PB103 - 9 x 6 44.95

PB104-9.5'x8 54.95

PB203 - 9.75 x 6V 2 x 2Va 75.00

PB203A - 9.75 x 6V 2 x 2% 124.95
(includes power supply)

PROTO CLIPS

14 PIN $4 50

16 PIN 4 75

24 PIN 8.50

40 PIN 13.75-

iMfc

Milium,

134

(W/l$

7400 TTL

SN740ON
SN7401N
SN7402N
SN7403N
SN7404N
SN7405N
SN7406N
SN7407N
SN7408N
SN7409N
SN7410N
SN7411N
SN7412N
SN7413N
SN7414N
SN7416N
SN7417N
SN7420N
SN7421N
SN7422N
SN7423N
SN742SN
SN7426N
SN7427N
SN7429N
SN7430N
SN7432N
SN7437N
SN7438N
SN7439N
SN7440N
SN7441N
SN7442N
SN7443N
SN7444N
SN7445N
SN7446N
SN7447N
SN7448N
SN7450N
SN7451N
SN7453N
SN7454N
SN7459A
SN7460N
20% Discount

16
18
18
18
18
20
29
29
20
20
18
25
25
40
70
25
25
20
29
39
25
29
29
25
39
20
25
25
25
25
20
89
49
75
75
75
69
59
79
20
20
20
20
25
20
100 pes

SN7470N
SN7472N
SN7473N
SN7474N
SN7475N
SN7476N
SN7479N
SN7480N
SN7482N
SN7483N
SN7485N
SN7486N
SN7489N
SN7490N
SN7491N
SN7492N
SN7493N
SN7494N
SN7495N
SN7496N
SN7497N
SN74100N
SN74107N
SN74109N
SN74116N
SN74121N
SN74122N
SN74123N
SN74125N
SN74126N
SN74132N
SN74136N
SN74141N
SN74142N
SN74143N
SN74144N
SN74145N
SN74147N
SN74148N
SN74150N
SN74151N
SN74152N
SN74153N
SN74154N
SN74155N
SN74156N
SN74157N
combined order

29
29
35
35
49
35

5 00
50
99
59
79
35

1 75
45
59
43
43
65
65
65

300
89
35
59

1 95
35
39
49
49
49
75
75
79

295

295
79

1 95

1 29
89
59
59
59
99
79
79
65

25%

1000

SN74160N

SN74161N

SN74162N

SN74163N

SN74164N

SN74165N

SN74166N

SN74167N

SN74170N

SN74172N

SN74173N

SN74174N

SN74175N

SN74176N

SN74177N

SN74179N

SN74180N

SN74181N

SN74182N

SN74184N

SN74185N

SN74186N

SN74188N

SN74190N

SN74191N

SN74192N

SN74193N

SN74194N

SN74195N

SN74196N

SN74197N

SN74198N

SN74199N

SN74S200

SN74251N

SN74279N

SN74283N

SN74284N

SN74285N

SN74365N

SN74366N

SN74367N

SN74368N

SN74390N

SN74393N

pet eombined

1 95

1 25

1 95

1 59

600

1 25

1 95

995

3 95

1 25

1 49

495

1 79

225

395

3 95

1 95

order

BUGBOOK

Continuing Education Sej

fhe

n*S22a

THE 555 TIMER APPLICATIONS $6 95

SOURCEBOOK WITH EXPERIMENTS
by Howard M Berlin W3HB

Thit Book snows you what tne 555 timer is ana no* lo use it Included are over
100 various desrgn techniques equations and graphs to create ready to go
timers generators power suopMes measurement and control circuits party
games circuits tor the home and automobile photography music and
Amateur Radio

INSTRUCTOR S MANUAL S3 00

Necessary tor instruction ot Bugooot I and II Answers questions regarding
experiments suggestions tor turther reading philosophy ot authors approach to
digital electronics A must tor sett teaching individuals

OP AMP MANUAL by Howard M Berlin W3HB SB. 00

An experiment guide to application ot operational amplttiers Over 25 enpen
ments on alt phases ot Op Amps

BUGB00KS I and II $17 00 per sat

ky Pater n R*ay. Dtvtd 6 Lanwe WdAHTj

Sold as a sat these two books outline over 90 experiments designed to teach
the reader alt he will need to know about TTL iog>c chips to use them m con
lunction with microprocessor systems You II learn about the basic concepts ot
digital electronics including gates hip hops latches buses decoders mult.
pktKtrs demultiplexers LEO displays RAM s ROM s and much much more

BUGBOOK He S5 00

ky Peter A Aewy Peine fi Lane*. WMHYJ

This volume will introduce you to the tabuious UAHT chip — that all important
interface between data terminals etc and your microcomputer It also covers
current loops and the RS ?3?C interface standard Particulany recommended
lor any RTTY enthusiast

BUGBOOK III J1580

by Peter ft Ratty. Oevti G LaitM. WB4HYJ. Jaaaftaa A Tltei
Here rs the book that puts n an together Besides naving much valuable text
there are a series ot eipenments m which the reader completely explores the
80e0 chip pin by pin and introduces you to the Marti SO microcomputer a
unique easily interlaced system It is recommended that you have the back
ground on the BUGBOOK S I 4 ll before proceeding with BUGBOOK III

BUGBOOK V and VI SIB 00 per set

by Oevie e Laraaa. Peter ft rVetty. Jaaaake* A Tttm
Expenmenis in digital electronics 9080A microcomputer programming and
BOS0A microcomputer mtertactng An integrated approach to sett instructed
banc digital electronics breadboardmg and atMOA interlacing programmmg
Hugbook VI integrates the digital concepts of Bugbook V into a treatment of
8O80A microcomputer programming and interfacing Detail 4 laboratory
experiments included with each book

DBUG

9080 interpretive

assembly language programs

$5 00

A program tor entering debugging and storing

CMOS M — DESIGNERS PRIMER $8 50

AND HAN0BO0K New expanded version

Starts at base structure of CMOS devices thiouqh integration into MSI

COMPLETE MANUAL FOR DIGITAL CLOCKS by John Weiss and John Brooks

Familiarizes technician or hobbyist with basic theories behind digital clocks Includes trouble shooting guides basic
characteristics ol clocks soldering techniques, clock component data sheets and construction tips

$3 95

CO4O00
CD4001
C04002
CD4006
CD4007
CD4009
C04010
CD4011
CO4012
CD4013
CD4014
CD4015
CD4016
CD4017
CD4018
CD4019
C04020
CD4021
CO4022
CD4023
CD4024
CO4025
CD4026
CD4027

1 19

1 39

1 19

1 39

1 19
23
79
23

2 25
69

C/M0S

CD4028
CD4029
CD4030
CD4035
CD4040
CD4041
CD4042
CD4043
CD4044
CD4046
CD4047
CD4048
CD4049
CD4050
CD4051
CD4053
CD4056
CD4059
CD4060
CD4066
CD4068
CD4069

1 19

1 25

1 79

2 50
1 35

1 19

295

995

1 49

CD4070

CD4071

CD4072

CD4076

CD4081

CD4082

CD4093

CD4098

MC 14409

MC14410

MC14411

MC14419

MCI 4433

MC14506

MCI 4507

MCI 4562

MC 14583

CD4508

CD4510

CD4511

C04515

CD4518

CD4520

CD4566

55
23
49

1 39
23
23
99

2 49
14 95
14 95
14 95

495

19 95

14 50

350

3 95
1 39

1 29

2 95
1 29

1 29

2 25

"74C0T"
74C02
74C04
74C08
74C10
74C14
74C20
74C30
74C42
74C48
74C73
74C74

- 3T -

65
300

65
2 15
4 75
1 50
1 15

74C00

74C85

74C90

74C93

74C95

74C107

74C151

74C154

74C157

74C160

74C161

3 95
300
200
200

1 25
290
300

2 15
325
325

74C163

74C164

74C173

74C192

74C193

74C195

74C922

74C923

74C925

74C926

80C95

80C97

300
325
260
3 49
2 75
275
995
895
14 95
11 95
1 50
1 50

78MG

LM300H

LM301CN/H

LM302H

LM304H

LM305H

LM307CN/H

LM308CN/H

LM309H

LM309K

LM310CN

LM311N/H

LM312H

LM317K

LM318CN/H

LM319N

LM320K-5

LM320K-5.2

LM320K-12

LM320K-15

LM320K-18

'J4ZIIX.1*.

LM320T-5

LM320T-5 2

LM320T-8

LM320T-12

LM320T 15

LM320T 18

LM320T-24

LM323K 5

LM324N

LM339N

LM340K-5

LM340K-6

LM340K-8

LM340K-12

LM340K-15

LM340K 18

LM340K 24

LM340T-5

1 75
80
35
75
1 00
60
35
1 00
1 10
1 25
1 15
90
200
650
1 50
1 30
1 35
1 35
1 35
1 35
1 35
'.IS.
1 25
1 25
1 25
1 25
1 25
1 25
1 25
595
1 80
99
1 35
1 35
1 35
1 35
1 35
1 35
1 35
1 25

LINEAR

LM340T-6

LM340T-8

LM340T 12

LM340T-15

LM340T-1B

LM340T-24

LM350N

LM351CN

LM370N

LM373N

LM377N

LM3B0N

LM380CN

LM381N

LM382N

NE501N

NE510A

NE529A

NE531H/V

NE536T

nULVHU

NE544N

NE550N

NE555V

NE556N

NE560B

NE561B

NE562B

NE565N/H

NE566CN

NE567V/H

NE570N

LM703CN/H

LM709N/H

LM710N

LM711N

LM723N/H

LM733N

LM739N

1 25

1 00

1 15

325

400

1 25

1 79

800

600

495

395

600

6QQ

4 95

1 30

500

1 25

1 75

10 50

1 00

1 19

LM741CN/H

LM741-14N

LM747N/H

LM748N/H

LM1303N

LM1304N

LM1305N

LM1307N

LM1310N

LM1351N

LM1414N

LM1458CN/H

MC1488N

MC1489N

LM1496N

LM1556V

MC1741SCP

LM2901N

LM3053N

LM3065N

35
39
79
39
90
1 19

1 40
85

2 95
1 65
1 75

59
1 95
1 95

1 75
300

2 95
1 50

l M1900NI 14011 49

LM3905N

LM3909N

MC5558V

LM7525N

LM7534N

8038B

LM75450N

75451CN

75452CN

75453CN

75454CN

75491 CN

75492CN

75494CN

RC4136

RC4151

RC4194

RC4195

1 25

495

1 25

595

4 49

74LSOO
74LS01
74LS02
74LS03
74LS04
74LS05
74LS08
74LS09
74LS10
74LS13
74LS14
74LS15
74LS20
74LS21
74LS22
74LS26
74LS27
74LS28
74LS30
74LS32
74LS37
74LS40
74LS42
74LS47

23
23
23
23
29
29
23
29
23
49
99
29
23
29
29
29
29
29
23
29
35
29
69
6.9

74LS00 TTL

74LS51

74LS54

74LS55

74LS73

74LS74

74LS75

74LS76

74LS83

74LS85

74LS86

74LS90

74LS92

74LS93

74LS95

74LS96

74LS107

74LS109

74LS112

74LS123

74LS132

74LS136

741S138

23
23
23
35
35
49
35
75
99
35
49
59
59
79
89
35
35
35
99
79
39
69

74LS13t»
74LS151
74LS155
74LS157
74LS160
74LS161
74LS162
74LS163
74LS164
74LS175
74LS181
74LS190
74LS191
74LS192
74LS193
74LS194
74LS195
74LS253
74LS257
74LS260
74LS279
74LS367
74LS368
74LS670

69
69
69
69
89
89
89
89
99
79

249
89
89
89
89
89
89
79
69
55
59
59
59

1 95

125

XC209

Red

XC209

Green

XC209

Yellow

200

XC22

Red

XC22

Green

XC22

Yellow

dta

dia

5/S1

4/$1
4/S1

5/S1
4/S1
4/S1

DISCRETE LEDS

XC111
XC111
XC111
XC111

dia
5/S1
4/S1
4 Si
4/S1

dia

XC526
XC526
XC526
XC526
XC526

185

Red

Green

Yellow

Clear

dta

5/S1
100/S8

4/S1

4 /SI
4/$1

XC556
XC556
XC556
XC556
XC556

200

Red

Green

Yellow

Clear

dia

5/S1

100/S8

4/S1

7/S1

190

Red
Green
Yellow
Clear

0S5
MV50 Red 6 Si

17r dia
MV10 Red 4$1
INfRA RED LED
1 1 16
5 $1 00

WIRE-WRAP KIT — WK-2-W
WRAP • STRIP • UNWRAP

• Tool for 30 AWG Wire

• Roll of 50 Ft White or Blue 30 AWG Wire

• 50 pes each 12 3 4 4 lengths —
pre -stripped wire

$12.95

WIRE WRAP TOOL WSU-30
WRAP • STRIP • UNWRAP $6.95

WIRE WRAP WIRE — 30 AWG

25ft mm $1 25 50ft $1 95 100ft $2 95 1000ft $15 00
SPECIFY COLOR — White - Yellow Red - Green • Blue - Black

WIRE DISPENSER — WD-30

• 50 ft roll 30 AWG KYNAR wire wrap wire $3.95 BZ.

• Cuts wire to desired length

• Strips 1 of insulation Sptctfy — Blue Yellow -White -Red

REPLACEMENT DISPENSER SPOOLS FOR WD 30

Specify blue, yellow, white or red

$1 98 /spool

Hal

DISPLAY LEDS

TYPE POLARITY

MAN 1 Common Anode -red
MAN 2 5 x 7 Dot Matrix -red
MAN 3 Common Cathode-red
MAN 4 Common Cathode -red
MAN 52 Common Anode -green
MAN 72 Common Anode red
MAN 74 Common Cathode-red
MAN 82 Common Anode-yellow
MAN 84 Common Cathode-yellow
MAN 3620 Common Anode -orange
MAN 3630 Common Anode-orange 1 1
MAN 3640 Common Cathode -orange
MAN 4610 Common Anode-orange
MAN 4640 Common Cathode-orange
MAN 4710 Common Anode-red 1 1
MAN 4730 Common Anode-red
MAN 4740 Common Cathode-red
MAN 4810 Common Anode -yellow
MAN 6610 Common Anode- orange -D D
MAN 6630 Common Anode -orange
MAN 6640 Common Cathode orange -D D
MAN 6650 Common Cathode-orange I 1
MAN 6660 Common Anode -orange
MAN 6680 Common Cathode -orange
MAN 6710 Common Anode - red -D D

HT PRICE TYPE POLARITY

270 2 95 MAN 6730 Common Anode-red * 1

300 4 95 MAN 6740 Common Cathode-red-D.D

125 25 MAN 6750 Common Cathode-red ± 1

187 195 MAN 6760 Common Anode-red

300 1 25 MAN 6780 Common Cathode-red

300 99 DL701 Common Anode-red * 1

300 125 DL704 Common Cathode-red

300 99 DL707 Common Anode-red

300 99 0L741 Common Anode -red

300 99 DL746 Common Anode-red t 1

300 99 DL747 Common Anode-red

300 99 DL749 Common Cathode-red • 1

300 99 DL750 Common Cathode -red

400 99 DL33B Common Cathode-red

400 99 FND70 Common Cathode

400 99 FND359 Common Anode

400 99 FND503 Common Cathode (FND500I

400 99 FND507 Common Anode (FND510)

560 99 5082-7730 Common Anode-red

560 99 HDSP-3400 Common Anode red

560 99 ADSP-3403 Common Cathode red

560 99 5082-7300 4 x 7 Sgl Dtgir-RHDP

560 99 5082-7302 4 x 7 Sfll Oigtt-LHDP

560 99 5082-7304 Overrange character l • 1)

560 99 5082 7340 4 x 7 Sgl Digit -Hexadecimal

560
560
560
560
560
300
300
300
600
630
600
630
600
110
250
350
500
500
300
800
800
600
600
600
600

PRICE

1 25

1 49

1 30
210

2 10
19 95
1995
1500
22 50

RCA LINEAR

CA3013
CA2023
CA3035
CA3039
CA3046
CA3059
CA3060
CA3080
CA3081

15
56
48
35
30
25
25
85
00

CA3082
CA3083
CA3086
CA3089
C A3 130
CA3140
CA3160
CA3401
CA3600

00
60
85
75
39
25
25
49
50

CALCULATOR CHIPS
AND DRIVER

FCM3817 (1998A) $ 5.00

MM5725 2 95

MM5738 2 95

DM8864 2 00

DM8865 100

DM8887 75

DM8889 75

CLOCK CHIPS

MM5309
MM5311
MM5312
MM5314
MM5316
MM5318
MM5369
MM5387
MM5841

$9 95
4 95
495
495
6 95
9 95
295
495
995

9374 - 7-segment LED driver
rnmmnnanntteLEDsS .99

IC SOLDERTAIL — LOW PROFILE (TIN) SOCKETS

8 ptn LP
14 pin LP
16 pin LP
18 ptn LP
20 ptn LP

14 ptn ST
16 pm ST
18 pin ST
24 ptn ST

Spin SG
14 pin SG
16 pin SG
18 ptn SG

8pm WW
10 pm WW
14 pm WW

16 pin WW
8 pin WW

1-24
$17
20
22
29
34

S27
30
35
49

$30
35
38

$40
45
39
43

25-49
16
19
21
28
32

25
27
32
45

27
32
35

38
41
38
42

50-100
15
18
20
27
30

24
25

30
42

24
29
32
43

35
37

37
41

1-24
22 ptn LP S 37
24 pm LP 38
28 pin LP <5
36 pm LP 60

SOLDERTAIL STANDARD (TIN) *° ■*" LP a

28 pin ST S 99
36 pm ST 1 39
40 pin ST 1 59

SOLDERTAIL STANDARD (GOLD)

24 pin SG $ 70

28pmS6 1-10

36pmSG 175

40 pin SG ^75

WIRE WRAP SOCKETS
(GOLD) LEVEL #3

22 pm WW $ 95
24 pin WW 1 05
28 pin WW 140
36 pin WW 159
40 pm WW 175

25-49
36
37
44
59
62

90
1 26
1 45

63
1 00
1 40
1 59

95
1.25
1 45
1 55

50-100

35
36
43
58

81
1 15
1 30

90
1 26
1 45

75
85

1 10
1 30
140

50 PCS. RESISTOR ASSORTMENTS $1 .75 PER ASST.

Ill OHM I? OHM If) OHM 18 OHM

OHM

ASST. 1
ASST. 2
ASST. 3
ASST. 4
ASST. 5
ASST. 6
ASST. 7

5ea

5 ea

5ea

5 ea

13 OHM 19 OHM 47 OHM

61 I IMM

180 OHM
4/0 OHM

5 ea

Sea

W OHM
??0 OHM

-
18(lk

i m

100 OHM

.'-() OHM

B80 OHM
I 8k

l.'k

•
1 SM

120 OHM

1.10 OHM

H.'tl I IMM
-

I5K

100k

1.80k
1 8M

4 m

CHI OHM

•

h Hk

18K

47k
1,'llk

U<h\
8,'OK

5 I.M

1/4 WATT 5». 50 PCS

1/4 WATT 5*. 50 PCS

1/4 WATT 5*. SO PCS

1/4 WATT 5*. 50 PCS

ASST. 7 5 ea /M i IM I MM 4 /M iM 1/4 WATT B% 50PCS

ASST. 8R Includes Resistor Assortments 1-7 (350 PCS ) $9.95 ea.

$5.00 Minimum Order - U.S. Funds Only
California Residents - Add 6% Sales Tax

Spec Sheets - 254

1979 A Catalog Available— Sand 41 c stamp

ameco

ELECTRONICS

.1 I \MI still I HIIMI s ..I I .1.1. .tin.

PHONE

ORDERS

WELCOME

(415)592 8097

MAIL ORDER ELECTRONICS - WORLDWIDE
1021 HOWARD AVENUE. SAN CARLOS. CA 94070

Advertised Prices Good Thru November

JE22MA $14 95

Function Generator Kit
(includes chip. PC
Board and instructions)

EXAR

JE2206B $19.95

Function Generator Kit
(includes all components.
P C Board and instructions)

XR-L555 $1.50

Micro-Power version ot the
popular 555 Timer and directly
interchangeable Dissipates
1/1 5th the power and operates
down to 2 7 volts Perfect tor
oattery operation and CMOS cir-
cuits

XR2242CP $1.50

Precision timing circuit for
generating timing pulses in mi-
nutes, hours and days or up to
1 year by using two Reduces
cost of time delay circuits Basic
555 Timer with built-in 8-b't
Counter

XR205

XR210

XR215

XR320

XR555

XR556

XR567CP

XR567CT

XR1310P

XR1468CN

XR1488

8 40

4 40

1 55

1 25

1 30

3 85

1 39

XR1489
XR1800
XR2206
XR2207
XR2208
XR2209
XR2211
XR2212
XR2240
KR2264

1 39

3 20

4 40

3 85
520
1 75

5 25

4 35

3 45

4 25

XR2556
XR2567
XR3403
XR4136
XR4151
XR4194
XR4202
XR4212
XR4558
XR4739
XR4741

3 20
299
1 25

1 25

2 85

1 45
360

2 05
75

1 1«i
1 47

TYPC

1N746

1N751A

1N752

1N753

IN 754

1N959

1N965B

1N5232

1N5234

1N5235

1N5236

1N456

1N458

1N485A

1N4001

1N4002

1N4003

1N4004

ZENERS

VOLTS W

DIODES —

phice typ£

RECTIFIERS

33
5 1
56
6?
68
82
15
56
62
68
75
25
150
180
50PIV
100 PIV
200 PIV
400 PIV

400m
400m
400m
400m
400m
400m
400m
500m
500m
500m
500m

40m
7m

10m
1 AMP
1 AMP
1 AMP
1 AMP

1 00

6 1 00

5 1 00

12 1 00

IM400!

if*400b
1N4007
1N36O0
1N4148
1N4154
1N4305
1N4734
1N4735
1N4736
1N4738
1N4742
1N4744
IN1 183
1N1184
1N1185
1N1186
IN1 188

VOLTS

600 PIV
800 PIV

1000 PIV

15
50 PIV

100 PIV

150 PIV

200 PIV

400 PIV

1 AMP
1 AMP
1 AMP
200m

10m

25m
1*
1w

1w
1w

l«

35 AMP
35 AMP
35 AMP
35 AMP

35 AMP

PRICE

10 1 00

6 1 00

15 1 00

12 1 00

20 1 00

1 60

1 70

1 80

300

SCR AND FW BRIDGE RECTIFIERS

C36D
C38M
2N2328
M0A980 1
MOA 980 3

15A@400V
35A c» 600V
1 6A<S> 300V
12A(& 50V
12A(S 200V

SCRI2N1849)

SCR

PW BRIOGE REC

FW BRIDGE REC

$1 95

1 95

C106B1

MPSA05

MPSA06

1IS97

TIS98

TIS133

TIS135

40409

40410

40673

?N918

?N2219A

?N22?1A

2N2222A

2N2369

.'N2369A

MPS2369

2N2484

?N?906

2N2907

.'N?9?5

MJE2955

?N3053

50
30
t 00
1 00
I 00
1 00
1 00
1 75
1 75
1 75
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 25
1 00

TRANSISTORS

.'N3055

MJE3055

:>N339?

.'N3398

PN3567

PN3568

PN3569

MPS3638A

MPS3702

2N3704

MPS3704

2N3705

MPS37%

2N3706

MPS3706

2N3707

2N3711
'4A
'5A

2N3772

2N3823

2N3903

1 00

t 00

1 00

SIOO

5 1 00

1 00

2 25
1 00

4 1 00

?N3904
7N3905

N3tfM
2N4013
2N4123
PN4249
PN4250
7N4400
?N4401
?N440?
2N4403
.'N4409

MSOM
2H5087
:'N5088
.^5089
2N5129
PN5134
PN5138
.'N5139
?N5210
.'N5449

'N5951

1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
1 00
4100
4 1 00
1 00
1 00
1 00
1 00
1 00
1 00
00
00

5
5

b
5
3 1

CAPACITOR -

10 pt

22 pt

47 pi

100 pi

220 pi

470 pt

001 ml
0022
0047ml
01ml

19
05
05
05
05
05
05

12
12
12
12

10 99
04
04
04
04
04
04

VOLT CERAMIC
OISC CAPACITORS

100
03
03
03
03
03
035

CORNER

001/iF
004 7,i F
OliiF
022 M F
047,if
1*F

19
05
05
05
06
06
12

100 VOLT MYLAR FILM CAPACITORS
10 07 022ml 13

10 07 047ml 21

10 07 1ml 27

10 07 22mt 33

10 99
04
04
04
05
OS
09

11
17
23
27

• ?0*. DIPPED TANTALUMS (SOLID) CAPACITORS

1 35V

15 35V

22 35V

33 35V

47 35 V

68 35V

1 35V

28
INIA

47 50V

Ana

1 0/50V

3 3 50V

4 7/25V

10 25V

1050V

22 25V

22 50V

47 25V

47/50V

100 25V

100 50V

220/25V

220/50V

470/25V

• 33

1000/16V

2200 16V

23
23
23
23
23
23
23

17
17
17
17
17
17
17

1 5'35V

2 2 25V

3 3 25V

4 7 25V
6 8 25V

10 25 V

30
31
31
32
36
40
63

26
27
27
28
31
35
50

MINIATURE ALUMINUM ELECTROLYTIC CAPACITORS
Radial lead

13
14
12
13
13
14
15
20
17
21
20
30
28
41
29
50
62

47 25V
47 50V
1 16V
1 25V
1 50V
4 7 16V
4 7 25V
4 750V
10 15V
10-25V
1050V
47 50V
100 16V
100 25V
100 50V
220/ 16V
470 25V

15
16
15
16
16
15
15
16
14
15
16
24
19
24
35
23
31

13
14
13
14
14
13
13
14
12
13
14
21
15
20
30
17
28

too

035

075

06
13
17
22

21
22
22
23
25
29
40

10
11
10
11
11
10
10

09
10
12
19
14
18
28
16
26^

135

This new instrument has taken a giant step in
front of the multitude of counters now available.
The Opto-8000.1 boasts a combination of fea-
tures and specifications not found in units cost-
ing several times its price. Accuracy of ±0.1
PPM or better — Guaranteed — with a
factory-adjusted, sealed TCXO (Temperature
Compensated Xtal Oscillator). Even kits re-
quire no adjustment for guaranteed accu-
racy! Built-in, selectable-step attenuator, rug-
ged and attractive, black anodized aluminum
case (.090" thick aluminum) with tilt bail. 50
Ohm and 1 Megohm inputs, both with amplifier
circuits for super sensitivity and both
diode/overload protected. Front panel in-
cludes "Lead Zero Blanking Control" and a
gate period indicator LED. AC and DC
power cords with plugs included.

OPTOELECTRONICS, INC,

5821 NE 14 Avenue

Ft. Lauderdale, FL 33334

Phones: (305) 771-2050 771-2051

Phone orders accepted 6 days, until 7 p.m. Q3

SPECIFICATIONS:

Time Base— TCXO ±0.1 PPM GUARANTEED!

Frequency Range— 10 Hz to 600 MHz

Resolution— 1 Hz to 60 MHz; 10 Hz to 600 MHz

Decimal Point — Automatic

All IC's socketed (kits and factory-wired)

Display — 8 digit LED

Gate Times — 1 second and 1/10 second

Selectable Input Attenuation— X1, X10, X100

Input Connectors Type — BNC

Approximate Size— 3"h x 7 1 /2"w x 6 1 /2"d

Approximate Weight — 2 1 /2 pounds

Cabinet — black anodized aluminum (.090" thickness)

Input Power— 9-15 VDC, 115 VAC 50/60 Hz

or internal batteries
OPTO-8000.1 Factory Wired
OPTO-8000.1 K Kit

$299.95
$249.95

tfii-im m

ACCESSORIES:

Battery-Pack Option — Internal Ni-Cad Batteries and charging unit

$19.95

Probes: P-100 — DC Probe, may also be used with scope $13.95

P-101 — LO-Pass Probe, very useful at audio frequencies

$16.95
P-102 — High Impedence Probe, ideal general purpose
usage $16.95

VHF RF Pick-Up Antenna-Rubber Duck w/BNC #Duck-4H $12.50

Right Angle BNC adapter #RA-BNC $ 2.95

FC-50 — Opto-8000 Conversion Kits:

Owners of FC-50 counters with #PSL-650 Prescaler can use
this kit to convert their units to the Opto-8000 style case, includ-
ing most of the features.

FC-50 — Opto-8000 Kit $59.95

* FC-50 — Opto-8000F Factory Update $99.95
FC-50 — Opto-8000.1 (w/TCXO) Kit $109.95

*FC-50 — Opto-8000.1F Factory Update $149.95

* Units returned for factory update must be completely as-
sembled and operational

TERMS: Orders to U.S. and Canada, add 5% to maximum of $10.00 per order
for shipping, handling and insurance. To all other countries, add 10% of total or-
der. Florida residents add 4% state tax. C.O.D. fee: $1 .00. Personal checks must
clear before merchandise is shipped.

136

PLACE ORDERS TOLL FREE: Mmm\i5Si?mZiZ

800/421-5809 Continental U.S.

THE DISCONTINUED
:o* orotic KITS
ARE STILL AVAILABLE
WHILE SUPPLY LASTS'

MICROPROCESSORS

Z80

Z80A

CDP1802CD

2650

AM 2901

6502

6800

6802

8008-1

8035

8035-8

8080a

8085

TMS9900TL

8080A SUPPORT DEVICES

8212

8214

8216

8224

8224-4

8226

8228

8238

8243

8251

8253

8255

8257

8259

8275

8279

USRT

S2350
UARTS

AY5-1013A

AY5-1014A

TR1602B

TMS601 1

IM6402

IM6403

6800 PRODUCT

681 OP
6821 P
6828P
6834P
6850P
6852P
•860P
6862P
687 1P
5875P
J880P
68B10P

KIM

6102

6502

6520

6522

6530

6530-002

6530-003

6530-004

6530-005

6532

CHARACTER GENERATORS

Upper (-12*5)
Lower (-12 ±.5)
Upper (5volt)
Lower (5 volt)
Up Scan
Down Scan

2513

MCM6571

MCM6571A

PROM'S

1702A
2708

2716(5+12)1*1
2716 5v) INTL

2758(5v)

DYNAMIC RAMS

JJgj>/4116

2107B-4
TMS4027
MM5270
MM5280

STATIC RAMS

21L02

2101-1

2111-1

2112-1

2114L

TMS4044

4200A

1-24

1.50
1.75
2.95
3.25
2.95
9.50

10.50
8.95
9.95

10.95

FLOPPY DISC CONTROLLER

1771B01
1781

KEYBOARD CHIPS

AY5-2376
AY5-3600
MM5740
MM5743

16.95
20.00
25.00
17.95
19.95
20.00
11.95
16.95
25.00
12.95
20.00
21.00
10.00
23.00
49.95

2.90

4.65

2.75

4.30

9.95

2.75

6.40

8.00

7.50

20.00

6.45

20.00

75.00

18.50

10.95

5.25
8.25
5.25
5.95
9.00
9.00

4.00

6.60

11.25

16.95

8.65

11.00

9.25

12.00

28.75

8.75

2.50

6.00

8.00
11.95
10.00

9.25
15.95
15.95
15.95
15.95
15.95
17.95

6.75

9.75

10.95

5.00

8.95

25.00

38.00

23.40

16.00
4.00
3.95
4.00
4.50
3.60

25-99

1.20
1.50
2.60
3.00
2.65
8.00
9.00
8.00
8.75
9.25

39.95
69.95

13.75
13.75
18.00
18.00

¥ V

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1
* '.>* •* • *» " * '

EXPANDO 32 KIT

Uses 4115 (8Kx1)
Dynamic RAM's, can be
expanded in 8K increments
up to 32K.

8K $179.00

16K $255.00

24K $325.00

32K $400.00

i I V

*.rmm**AA** •< • ** >*i**

t^UMH I

EXPANDO 64 KIT
Uses 4116 (16Kx1)
Dynamic RAM's, can be
expanded in 16K increments
up to 64K.

16K $260.00

32K $579.00

48K $757.00

64K $925.00

ffccippkz u
w computer

One of the best "Total Package"
home and business computers on
the market. "Basic" in ROM,
Color Graphics, Floating Point
Basic Package, etc.

I6K version only $1,095.00

4116 (16K x 1- 300ns)
MEMORY EXPANSION KIT

Dynamic RAM chip can be
used for expanding APPLE II
or TRS-80. Instructions incl.

8 for $98.00

JADE PARALLEL/SERIAL
INTERFACE

S-100 compatible, 2 serial
I/O ports, 1 parallel I/O.
Kit JG-P/S $124.95

Ass. & Tested

JG-P/SA $179.95

Bare Board

with manual $30.00

FLOPPY DISK INTERFACE

JADE FLOPPY DISK (Tarbell
board)

Kit $175.00

Assm. & Tested $250.00

S.D. Computer Products
"Versa Floppy"
Kit $159.95

Assm. & Tested $189.95

EPR0M BOARD KITS

RAM'N'ROM

(16 K any EPROM) $117.00

MR-8 (1 K RAM, uses

2708) $99.50

MR-16 (1 K RAM, uses

2716) $99.50

EPM-1 (uses up to 4 K

of 1702) $59.95

JG8/16 (uses 2 70 8 or

2716) $59.95

THE PIGGY IS COMING!

MOTHER BOARDS,
S-100 STYLE

9-Slot "Little Mother"
Kit $85.00

Assm. & Tested $99.00

Bare Board $35.00

13-Slot with front panel slot
Kit $95.00

Assm. & Tested $110.00
Bare Board $40.00

22-Slot

Assm. & Tested $149.00

GOLD PLATED

S-100 EDGE CONNECTORS

Soldertail $3.25 each

10 for $30.00
Wire Wrap $4.50 each

10 for $40.00

Computer Products

4901 W. ROSECRANS AVENUE
Department "K"
HAWTHORNE, CALIF. 90250

Cards
Welcome

Cash, Checks, Money Orders, and Credit Cards
accepted. Add freight charge of $2.50 for orders
under 10-lbs. Add 6% sales tax on all parts
delivered in California. Discounts available at
OEM quantities.

WRITE FOR OUR FREE CATALOG !

JADE 8080A

with full documentation

Kit $100.00

Assm. & Tested $149.95
Bare Board $30.00

JADE Z80

with provisions for ONBOARD
2708 and POWER ON JUMP

2 MHz

Kit

Assm. & Tested

4 MHz
Kit
Assm. & Tested

Bare Board

$135.00
$185.00

$149.95
$199.95

$35.00

MD 690a CPU BOARD

S-100 Compatible 6800 MPU
1 K x 8 RAM, PROM
expandable to 10K.

$199.95

TU-i

Convert your T.V. set into a

Video Monitor

Kit $8.95

JADE VIDEO INTERFACE

S-100 Compatible Serial
Interface with Sockets Included.
Kit $117.95

Assm. & Tested $159.95

Bare Board with
manual $35.00

SHUGART DISK DRIVES

*Lm%

SA400

$295.00

Single-density 5V4", 3 5 track
drive.

SA801R $495.00

Single-sided 8" floppy disc
drive.

DM 2700-S $750.00

Includes SA801 R disk drive,
10" x 10" x 16" cabinet,
power supply, data cable, fan,
AC line filter.

STATIC RAM BOARDS
JADE 8K

Kit JG8K (4 50ns) $125.95

Assm. & Tested

JG8KA (250ns) $139.75

Kit JG8K (250ns) $149.75

Assm. & Tested

JG8KA (250ns) $169.75

Bare Board without

parts $25.00

16K -Uses 2114's (lo power)

Assm & Tested

RAM 16 (2 50 ns) $375.00

Assm. & Tested

16 B (4 50 ns) $325.00

Mem-2 Kit (2 50ns) $285.00

16K Static with memory
management

Assem.& Tested

RAM 65 (250ns) $390.00

Assm. & Tested

RAM 6 5 B (4 50 ns) $350.00

Seals 32K

Assm. & Tested

JG32 (2 50ns) $795.00

Assm. & Tested

JG3 2B (4 50 ns) $725.00

Kit JG32K (250ns) $575.00

137

♦ 279

16 K

of static S-100 memory

mum >

. . ffr^ty

njA

Our Econoram IV"" "unkit" comes with
sockets and bypass caps pre-soldered into place
for easy assembly. Plugs into any S-100 buss
machine. Features under 2000 mA current,
complete buffering, fully static operation, and
our enviable reputation for reliability under all
operating conditions.

Assembled and tested, $314; qualified under the CSC program*, $414.

*445

24 K

of static S-100 memory

Mlltlrt iWttfl

Econoram VIP is an "unkit" that has sockets
and bypass caps pre-soldered into place. This
full feature memory is configured as two 4K and
two 8K blocks for maximum flexibility, boasts
current consumption under 2000 mA, and
follows our design policy of fully static opera-
tion with complete buffering.

Assembled and tested, $485; qualified under the CSC program*, $605.

•(Certified Systems Components boards are assembled, tested, serial numbered, burned in for 200 hours, and
guaranteed to run at 4 MHz over the full temp range. We exchange board if failure occurs within / year of invoice
date.)

ATTENTmN-

# rad1oshack* ######
trs-80 and heath

J?. 8 ..?™. E .?. S . : ..........

MEMORY PRICES ARE
COMING DOWN!!

Our TRS-80 Conversion Kit chip sot is
now only $159 (3 kits for $450). It not only
upgrades your mainframe from 4K to 16K, but
can also populate the memory expansion
module with extra memory. Works with APPLE
computers too. We include full instructions for
the TRS-80 conversion, and back up our parts
with a 1 year warranty.

Heath H8 owners are recognizing that our
12K Econoram VT m , designed specifically for
the H8 buss, offers a superior memory value at
$235. Now you can buy two of our 12K
boards on special for $399 (price good
through cover month of this magazine). These
are "unkits" with sockets and bypass caps pre-
soldered in place. Need we say more?

MOTHERBOARDS

S135

of static S-100 memory

Econoram IT is our biggest selling kit to date,
thanks to the cost-effectiveness it brings to the
S-100 buss. Features low current consumption,
high speed, full buffering, and the same perfor-
mance that has made Econoram one of the best
selling peripherals in the business.

Of}*

muinnrn

Assembled: $155. Quantity kit price: 3/$375

ALL OF THE ABOVE ARE AVAILABLE FROM STOCK. Coming soon: 32K boards for the S-100
buss, the Intel /National 80/10 and 80/20, and the Digital Group . . . plus a dual UART S-100 I/O board
and our new family of S-100 Econorams. Watch this space, or inquire about price and availability.

ACTIVE

TERMINATOR

v*>9>3U (kit)

Active termination draws much less power than
passive termination, and minimizes the glitches,
noise problems, crosstalk, ringing, and other
gremlins that can occur with unterminated busses.
Plugs into any S-100 computer. Many have copied
our technique; few can match our low price.

ntimiimmmmmmuuuttummn
j !un iwinwimrmmmtmr

*'*??5f

CompuKit"

TERMS: Col res. add tax. Add 5% shipping, ex-
cess refunded COD orders OK with street address for
UPS. Visa* /Mastercharge® orders call our 24-hr.
order desk at (415) 562-0636 Thank you for your
business.

1 1 slots, with active termination circuitry, heavy
power/ground traces, and all edge connectors: $90
in "unkit" form (edge connectors are pre-soldered
in place, making assembly a cinch). Need more
slots? Our 18 slot motherboard "unkit" includes all
the above along with 18 edge connectors for $124.

MULLEN RELAY/
0PT0-IS0LAT0R CONTROL
00ARD $88 ,..,

8 reed relays respond to an 8 bit word (relays can also
drive Mullen 500 Watt AC control modules for power ap-
plications); 8 opto-isolators receive outside world signals
for handshaking or further control purposes. Applications
include audio, time lapse photography, robots; one user
even devised an automatic cat feeder. At our new low
price, you can afford to let your imagination run wild.

MULLEN EXTENDER BOARD

yuD (kit)

From Mullen Computer Products. We now carry the im-
proved version that includes a built-in "kluge board" area
in addition to the integral logic probe and ingenious edge
connector. Greatly simplifies servicing and testing . . .
when it comes to extender boards, it would be hard to im-
prove on this unit in terms of either price or ease of use.

BILL GODBOUT ELECTRONICS
BOX 2355, OAKLAND AIRPORT, CA 94614

138

S.D. COMPUTER PRODUCTS

AN EMPIRE INO CO

P.O. BOX 28810K

DALLAS, TEXAS 75228

EXPANDABLE EPROM BOARD

16K OR 32K EPROM $49 95 W/OUT EPROM
Allows You to Use Either 2708s For 16K of Eprom or
2716s For 32K of Eprom.

KIT FEATURES:

1. All Address Lines & Data Buffered

2. Quality Plated through PC. Board Including
Solder Mask and Silk Screen

3. Selectable Unit States

4. On Board Regulation Provided

5. All Sockets Provided W/ Board

WE CAN SUPPLY 450As 2708s AT $11.95
WHEN PURCHASED WITH BOARD.

EXPANDORAM
THE ULTIMATE RAM BOARD

32K FOR $475.00

yJr —

4K LOW POWER RAM KIT
The Whole Works - $79.95

Full Buffered - on board regulated - reduced
power consumption utilizing low power 21L02-1
500ns RAMS - Sockets provided for all IC's
Quality plated through PC board.

32K MODEL
8K $151.00

16K 259.00

24K 367 00

32K 475 00

THE 32K VERSION USES THE MOS
TEK MK4115 RAM AND HAS 8K
BOUNDARIES AND PROTECTION &
UTILIZES DIP SWITCHES P. C.
BOARD COMES WITH SOCKETS FOR
32K OPERATION

^^i^Pm"WfT

BUY A S100 COMPATIBLE RAM
BOARD AND UPGRADE THE SAME
BOARD TO A MAXIMUM OF 65K
MEMORY IN STEPS OF EITHER 8K
OR 16K AT YOUR OPTION BY MERE
LY PURCHASING MORE RAM CHIPS
FROM SD COMPUTER PRODUCTS

64K MODEL

16K $28100

32K 519.00

48K 757.00

64 K 995 00

THE 64K VERSION USES THE MOS
TEK MK4116 RAM AND HAS 16K
BOUNDARIES AND PROTECTION &
UTILIZES DIP SWITCHES P. C.
BOARD COMES WITH SOCKETS FOR
64K OPERATION

Low Cost

l- u.». I

Cassette
Interface Kit

*""* ,**.*.

$19.95

1 1 ' ~r...

h 1

Features Play and record K.C. Standard 2400/1200 Hi
tapes 300 Baud, TTL 1/0 Compatible, Phase Loch Loop,
Both 22 Pin Connector and 8 Pin Molex Connector.
Comes partially assembled Oscillator and phase lock
loop pre tuned to K.C. Standard Selector switch sends
cassette data or auxiliary input data to microprocessor.
LED indicates logic 1 level

•*J

Z -

•Add $10 00 tor
250ns RAM operation

HAVE BUILT INTO THE EXPANDORAM!

• NO WAIT STATES REQUIRED

• NO CYCLE STEALING NEEDED

• ON BOARD REGULATION

• CONTROL, DATA & ADDRESS INPUTS
UTILIZE LOW POWER SCHOTTKY
DEVICES

• DESIGNED TO WORK WITH Z-80,
8080. 8085. CPU's

ADD $50.00 TO ABOVE PRICES FOR FULLY ASSEMBLED AND TESTED BOARDS

LOOK AT THE FEATURES WE

MEMORY ACCESS TIME IS 375 ns
MEMORY CYCLE TIME IS 500 ns
POWER REQUIREMENTS ARE:
8 VDC 400 MA DC
18 VDC 400 MA DC
— 18 VDC 30 MA DC
ON BOARD INVISIBLE REFRESH

Z-80 CPU BOARD KIT
Complete Kit $139.

:jni

I i-*«>

CHECK THE ADVANCED FEATURES OF OUR Z-80
CPU BOARD: Expanded set of 158 instructions,

8080A software capability,
operation from a single
5VDC power supply; always
stops on an Ml state, true
sync generated on card (a
real plus feature!), dynamic
refresh and NMI available,
either 2MHZ or 4MHZ op-
eration, quality double sided plated through PC
board; parts plus sockets provided for all IC's.
*Add $10. extra for Z-80A chip which allows
4MHZ operation.

» i>

NEW FROM S.D.

"VERSAFLOPPY" KIT

THE VERSATILE FLOPPY DISK CONTROLLER
ONLY $149.00

FEATURES: IBM 3740 Soft Sectored Compatible. S-100 BUS
Compatible for Z-80 or 8080. Controls up to 4 Drives (single
or double sided). Directly controls the following drives:

1. Shugart SA400/450 Mini Floppy

2. Shugart SA800/850 Standard Floppy.

3. PERSCI 70 and 277.

4. MFE 700/750.

5. CDC 9404/9406.

34 Pin Connector for Mini Floppy. 50 Pin Connector for Stand
ard Floppy. Operates with modified CP/M operating system
and C Basic Comptler. The new "Versafloppy" from S.D.
Computer Products provides complete control for many of
the available Floppy Disk Drives, Both Mini and Full Size.
FD1771B-1 Single Density Controller Chip. Listings for Con-
trol Software are included in price.

FD 1771B 1 CHIP ALONE $39.95

8K LOW POWER RAM
$159.95

FULLY ASSEMBLED AND TESTED NOT A KIT
Imsai — Altair — S-100 Buss compatible, uses low power
static 21 L02 600ns fully buttered on board regulated,
quality plated through PC board, including solder mask 8
pos dip switches for address select

'Add $30.00 for
250ns RAM operation

Z80 STARTER KIT

LEARN COMPUTERS FROM THE START!
SIMPLE, STEP BY STEP LEARNING. CONSTRUCTION,
PROGRAMMING, OPERATION, MEMORIES, INTER-
FACING, COMPUTING, AND CONTROLLING WITH
AUDIO CASSETTE INTERFACE CAPABILITIES.

Complete Kit includes: Key board and Display; Z80
Central Processing Unit; Instructions; Operation Man-
ual; Learning Guides.

Features: Powerful Z80 CPU with 158 instructions • 1024
Bytes (Expandable to 2048 Bytes ON BOARD) of RAM •
2 Bi Directional Input/Output Ports with Handshaking

* Kansas City Standard Audio Cassette Interface for
Program Storage * Hexadecimal Keyboard and Display

• Wirewrap area for custom circuitry • S-100 Connector
on board for Memory and I/O Expansion • 2716/2758
PROM Programmer • "ZBUG" Monitor ROM (Including:
Memory, Port and Register Examine and Change Com-
mands; Breakpoints; Single Step Capability; Audio Tape
Load and Dump; Execute user program Commands.)

Many more unique features. The best computer edu-
cational kit on the market . . . the complete computer
and educational package for only $199.00. (Available
June 1978).

INTRODUCING THE SBC-100

(The Z-80 Based, S-100 Single Board Computer)

$349.00

FEATURES:

• No Front Panel Needed

• Z-80 CPU (2 or 4 MHZ)

• IK RAM

• 4 ROM/PROM Sockets for 4K/8K of Memory

• SYNCHRONOUS/ASYNCHRONOUS Serial I/O with
RS 232 and Current Loop Interface and Software

• Programmable Baud Rate

• Parallel Input Port

• Parallel Output Port

• 4 Channel Timer/Counter

• 4 Vectored Interrupts

RAMS

21L02-500NS
21L02 - 250NS
2114 - 4K
1101A - 256
1 1 03 — 1 K
MK 41 15 8K
74S 200 256

11 50
15 95
14 95
$4 00
J5
1€ 45
3 95

O. E.M. SPECIAL

ASK ABOUT SPECIAL OEM DISCOUNTS ON THE SD
SDC-lOO — SINGLE BOARD COMPUTER
VERSAFLOPPY'^' — FLOPPY DISK CONTROLLER
EXPANDORAM — 32K RAM

■COMPATIBLE SET ■

$349 OO
$149 OO
$475 OO

EACH KIT IF PURCHASED SEPARATELY TOTAL $973 OO
ORDER ALL 3 KITS TOGETHER FOR

$899.00

This Powerful Threesome Operates Together to Form A Comolete Computer for Your System.

Z-80

Programming Manual

IN DEPTH DETAIL OF

THE Z-80 CPU

MICRO-COMPUTER

S. D. SALES SPECIAL

$9.95

S.D. NOW HAS SOFTWARE FOR IT'S CUSTOMERS

CP/M DISK OPERATING SYSTEM

$99.95

CPU's

Z — 80 includes manual
Z — 80A includes manual
8080A CPU 8 BIT
8008CPU8 BIT

29 95
34 95

11 95
6 95

CP M is a powerful disk operating system which has become an industry standard. It is compatible with several
disk based FORTRAN and BASICS This package includes a CP/M diskette (mini or full size) adapted for S D s
SBC lOO/VERSAFLOPPY EXPANDORAM board set Complete documentation is included ( n CP/M is a reg
istered trademark of Digital Research Corp , Pacific Grove. CA

PROMS

1702A - IK - 1.5us 3.95 or 10/35.

2708 - 8K - 450ns 14.95

5204 - 4K 7.95

82S129 — IK 2.50

2708U 8K signetics 650ns 9 .95

COUNTER CHIPS

Z80 DISK BASED ASSEMBLER $69.95

Runs on ANY CP/M based disk system Assembles
the official Zilog Mostek Mnemonics Contains ex
tensive set of pseudo ops Available on mini or
full size diskette

SD MONITOR

$49.95

Powerful monitor for SBC lOO Single board com
puters Includes all VfcRSAFLOPPY control firm
ware Comes in 2716 prom. Available in 4 6 weeks

VERSAFLOPPY DIAGNOSTIC PROGRAM

$2495

VERSAFLOPPY CONTROL FIRMWARE

$24.95

MK50397 6 Digit elapsed timer 8 95

MK50250 Alarm clock 4.99

MK50380 Alarm chip 2.95

MK50395 6 digit up/dn. count. 12.95

MK5002 4 digit counter 8.95

MK5021-Cal. chip sq. root 2.50

Provides control for VERSAFLOPPY and boots up
CP/M This runs on Z 80. 8080 or 8085 based
computers Available in 2708 or 2758 prom.

Provides routines which are helpful in checking out
a disk based system Available in 2708 or 2758
prom

SUPER FLOPPY SPECIAL

S. D. SALES' VERSAFLOPPY S 100 CONTROLLER BOARD PLUS
SHUGART SA 400 FLOPPY DISK DRIVE INCLUDING CABLE FOR ONLY

$479.00

MICROPROCESSOR
CHIPS

8212 - 1/0 port

8214 — P.I. C

8216 — Non Invert Bus . .

8224 — Clock Gen

8226 — Invert Bus

PI0 for Z— 80

CTC for Z— 80

8228 Sys. Controller
8251 Prog. comm. interfact
8255 prog. prep, interface

8820 Dual Line Recr

8830 Dual Line Dr

2513 Char. Gen

8838 Quad Bus. Recvr. . .
74LS138N — 1/8 decoder
8T97-Hex Tri State Buffer

1488/1489 RS232

TR 1602B Uart

TR 1863 Uart

FD 1771B-1

. 3.50

12.95

4.95

495

3.95

14.95

8.20

1095

13.50

1.75

.1.75

7.50

2.00

.99

1.25

.1.50

3.95

8.50

39 95

CMOS

4001
4002
4011
4013
4016
4017
4020
4022
4024
4027

19
19
19
32
32
95
97
97
75
39

4029

4042

4047

4049

4069

4071

4076

14518

14528

14529

99
69

1 50
35
23
19
97

1.10
85
85

CALL IN YOUR BANKAMERICARD
(VISA) OR MASTER CHARGE OR-
DER IN ON OUR CONTINENTAL
TOLL FREE WATTS LINE:

1— 800—527—3460

Texas Residents Call Collect:

214/271—0022

DEALER INQUIRIES INVITEDI

(All prices subject to change
without prior notice )

NO COD's. TEXAS RESIDENTS ADD
5% SALES TAX ADD 5% OF ORDER
FOR POSTAGE & HANDLING OR
DERS UNDER $10 ADD 75c HAND
LING FOREIGN ORDERS - U. S
FUNDS ONLY»

*2»

COMPUTER
SPECIALS

WE'VE^GOT A TRUCKLOAD COMING!
. . . and it's COLOR

"The Compucolor II"

... a personal colorgraphics system for the modern computer man . . .

• Color Graphics 1 3" Color CRT ^^ ,

• Proven 8080A CPU System

• 1 6K Extended Disk Basic

• Up to 1 1 7* Key Keyboard

• Up to 32K* RAM

• Minidisk Drive 51. 2K Bytes/Side ~^^Z^^^ 'options
Order your system now and we will include at no cost

(2) Programmed Software Diskettes ($39.90 value)
Model 3 with 8K RAM 72 Key Keyboard/RS232 . . $1 495
Model 4 with 16K RAM & RS232C port plus 72 Key
Keyboard $1 795.00

Model 5with32KRAM,RS232Cand 72 Key Keyboard $2395.00

Options: Add $ 1 00.00

101 Key Keyboard Add $1 50.00

1 1 7 Key Keyboard Add $225.00

Programmed Diskettes $1 9.95 each

Formatted Diskettes 2/$1 9.95

EXIDY SORCERER

Regular Price $895.00
Special Introductory Price
67QA aa Limit one per
W * W« W customer.

• W/16K $1150.00

• W/32K $1395.00
Combines

the desirable features of the

PET, APPLE and TRS-80 into a

complete expandable computer

system. If you are a comparison

shopper send for comparison

chart.

• INCLUDES:
Keyboard & enclosure totally
assembled

90 day Warranty
8K BASIC (MICROSOFT)
Video & Cassette Cable
Complete Documentation
** S100 Expansion

Module Add $299.00

** Cassette recorder

Add $44.95

• • Sanyo 9" Monitor

Add $169.95

KIM-1 r-?^

Now only C' J _

$229.95 ,J^'<£d

Regular price ^„
$245.00

The KIM-1 6502 Standard
Computer System now available
off the shelf. Write for complete
details and software package.

** Power Supply

Add $59.95

** Cassette Recorder

Add $44.95

• • Sanyo 9" Monitor

Add $169.95

VIM-1

"The Ultimate in
Single Board Low-Cost
Computers" In Stock

$269.00

• KIM-1 Compatible

• 4K ROM Monitor

• 1 KBytes 21 14 RAM

it 65K Memory Expansion

• UserEPROM 2716
** Power Supply

Add $59.95

** Cassette Recorder

Add $44.95

*• Sanyo 9" Monitor

Add $169.95

School & group discounts
available.

AIM-1

SSSS" " 1 * 1,

Singleboard Computer

• On Board 20 column
alphanumeric printer

• Alphanumeric 20 character
display

• Terminal style Keyboard
54 Keys

• 6502 based CPU

w/1 K RAM $375.00

w/4K RAM $450.00

Assembler ROM . . . Add $85.00
BASIC Interpreter in ROM
Add $100.00

RCA

COSMAC VIP

CO*«AC VIP

I NEW LOW PRICE $249. 00 1
Assembled
Regular price $299.95

w/Sanyo 9" Monitor
Add $169.95

"Now you can afford to
experiment using RCA's fine
1802 CMOS CPU."

PRINTERS

OKIDATA Model 110 w/tractor W/RS232

$1675.00

OKIDATA Model 22 w/tractor W/RS232

$2705.00

DECWRITER II W/RS232 10-30cps

$1475.00

DIABLO 1620-3 w/tractor feed,

w/Keyboard $3255.00

DIABLO 1610-3 w/tractor feed $2995.00
IPSI 1 622-3 w/tractor feed

(diablo compatible) $2995.00

IPSI 161 2-3 w/tractor feed

(diablo compatible) $2820.00

Centronics 761 (KSR) $1 595.00

Centronics Micro P-1 $395.00

Centronics 761 RO $1 495.00

Centronics 779 w/tractor feed ... $1 195.00
Teletype Model 43 W/RS232 ... $1 1 99.00
Tl Model 745 w/upper and lower case
$1975.00

FLOPPY DISK'S

Shugart SA400 Minifloppy Disk Drive
$325.00

Shugart SA450 Dual Density Minifloppy

$375 00

Shugart SA800/801 Diskette
Storage Drive $495.00

Shugart SA850/851 Double-Sided
Drive $625.00

NORTH STAR HORIZON

Now in stock North Star Z-80 based high-performance computer.
it Z-80 Processor

• Motherboard

• 2 Serial +1 Parallel Port

• 16KRAM

Horizon I .
Horizon II.

$1439.00 Kit
$1799.00 Kit

MFE Mayflower Model 751 Double

Density $730.00

Persci Model 277 Dual Diskette

Storage Drive $1 230.00

Pertec FD200 Miniflop Disk Drive $299.00
Pertec Model 88 8" Drive $495.00

Calcomp Model 143M Dual Density

Drive $625.00

North Star MDS Minifloppy w/S-100

$599.00

TERMINALS

SOROC IQ 1 20 $895.00

LEAR ADM3 Assembled $829.95

LEAR ADM3 Kit $739.95

SOROC IQ 140 $1495.00

Sanyo 9" Monitor $159 95

Sanyo 1 5" Monitor $209 95

Motorola 1 2" Monitor w/o chassis

j2 1 9 95

Hazeltine 1 500 $1095.00

Hazeltine 1510 $1295 00

KEYBOARDS

GEO Risk Model 756 ASCII 56 Key

Assembled $67.95

Metal case for Model 756 $27 00

Clare Pender 62 Key ASCII w/26 Pin
and 34 Pin Connector

(new surplus supply limited) $54.95

63 Key Unencoded Keyboard $32.95

10 Key Hexpad Unencoded $1 1.95

ADVANCED COMPUTER PRODUCTS

P. O. Box 17329 • Irvine, California 92713
1310 B E. Edinger • Santa Ana, California 92705
TWX/TELEX 910 595 1565 • TEL (714) 558-8813

All prices FOB Santa Ana. Please add shipping/
handling. For credit card purchase contact for
quotation. Complete FREE 1978 Catalogue -
send 25C for postage.

140

HE ALL NEW SYM-1** MICROCOMPUTER
BY SYNERTEK SYSTEMS CORP.

F YOU LIKE KIM* YOU WILL LOVE SYM

SYM-1 PROVIDES YOU WITH ON-BOARD EXPANSION,
"he printed circuit board includes sockets to add additional
IOM, PROM, RAM, or Peripheral Ports when you require
:hem.

iUPER SOFTWARE

Synertek has enhanced KIM-1* software as well as
lardware. The software has simplified the user interface,
"he basic SYM-1 system is programmed in machine language,
lonitor status is easily accessible, and the monitor gives
the keypad user the same full functional capability of the
user.

This is the newest, most advanced 6502-based system
lvailable on the market today. The SYM-1 is hardware
:ompatible to the KIM-1*. The manual even provides a
:ross-reference table to help convert KIM-1* software for
jse on the SYM-1 . The SYM-1 has everything the KIM-1 * has
to offer, plus so much more that we cannot begin to tell you
lere. So, if you want to know more, the SYM-1 User Manual

"Because of a name conflict, the VIM-1 will now be called the
SYM-1.

is available, separately, or, see page 1 24, June, 1 978 issue

of KILOBAUD magazine.

SYM-1 complete w/manuals $269.00

SYM-1 User Msnual Only $7.00

EXPANSION BOARDS FOR SYM-1 & KIM-1*

These boards are set up for use with a regulated power supply such as the one below, but, provisions have been made so
that you can add onboard regulators for use with an unregulated power supply. But, because of unreliability, we do not
recommend the use of onboard regulators. All I.C.'s are socketed for ease of maintenance. All boards carry full 90-day warranty.

I-SLOT MOTHERBOARD

This motherboard uses the KIM-4* bus structure. It
Iprovides eight (8) expansion board sockets with rigid card
supports, jacks for audio cassette, and fully buffered.
VAK-1 motherboard $129.00

2708 EPROM PROGRAMMER

This board requires a +5 VDC and -M2 VDC, but has a

DC to DC multiplyer so there is no need for an additional

I power supply. All software is resident in on-board Rom, and

has a zero-insertion socket.

VAK-5 2708 Eprom Programmer $269.00

16K STATIC RAM BOARD

This board using 2114 Rams is configured in two (2)
separately addressable 8K blocks with individual write-
protect switches.

VAK-2 16K Ram Board with only $239.00

8K of Ram [Vz populated)
VAK-3 Complete set of chips to $175.00

expand above board to 16K
VAK-4 Fully populated 16K Ram $379.00

EPROM BOARD

This board will hold 8K of 2708 or 2758, or 1 6K of 271 6
or 2516 Eproms. Eproms not included.
VAK-6 Eprom Board $129.00

POWER SUPPLIES

ALL POWER SUPPLIES

are totally enclosed with grounded enclosures for safetv, AC power cord, and carry a full 2-year warranty.

FULL SYSTEM POWER SUPPLY

This power supply will handle a microcomputer and

up to 65K of our VAK-4 RAM. ADDITIONAL FEATURES ARE:

Over voltage Protection on 5 volts, fused, AC on/off switch.

FNTFRPRISES Equivalent to units selling for $225.00 or more.

L- IN I t II I II I W I— KJ p rov i d es +5 V. DC @ 10 Amps & ±12 V. DC @ 1 Amp

VAK-EPS Power Supply $125.00

INCORPORATED

2967 W. FAIRMOUNT AVE.

PHOENIX, ARIZONA

85017

(602) 265-7564

R20

KIM-1* Custom P.S. provides 5 V. DC @ 1.2 Amps

and+12 V. DC @ .1 Amps
KCP-1 Power Supply

SYM-1 Custom P.S. provides 5 V. DC @ 1.4 Amps
VCP-1 Power Supply

$41 .50

$41.50

*KIM is a product of MOS Technology

ON ALL OF THE ABOVE ITEMS DEL/VERY IS FROM STOCK

141

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. • • • •

1tew

KfT FEATURES:

16K E-PROM CARD

IMAGINE HAVIN6 16K OF SOFTWARE ON LINE AT ALL TIME!
S-100 llmsai/Altair] Buss Compatiile!

1. Double sided PC board with solder
mask and silk screen and gold plated
contact fingers.

2. Selectable wait states.

3. All address lines & data lines buf-
fered!

4. All sockets included.

5. On card regulators. •

KIT INCLUDES ALL PARTS AND
SOCKETS (except 2708s). Add $25. for
assembled and tested.

PRICE CUT!

$57.50 kit

SPECIAL OFFER:

WAS $69.95

Our 2708s (450NS) are $8.95
when purchased with above kit.

iA Su T

KIT FEATURES:

ADD

$20 FOR

250 NS

1. Doubled sided PC Board with solder
mask and silk screen layout. Gold
plated contact fingers.

2. All sockets included.

3. Fully buffered on all address and
data lines.

4. Phantom is jumper selectable to

fin 67.
OUR 7805 regulators are provided

""* (450NS)

BK LOW POWER RAM KIT $149 00

S-100 (Imsai/Altair) Buss Compatible!

USES 21 L02 RAM'S!

2 KITS FOR $279

Fully Assembled & Burned In

$179.00

Blank PC Board w/ Documentation

$29.95

Low Profile Socket Set 13.50

Support IC's (TTL & Regulators)

$9.75

Bypass CAP's (Disc & Tantalums)

$4.50

MOTOROLA QUAD OP - AMP

MC3401. PIN FOR PIN SUB.
FOR POPULAR LM 3900.

3 FOR $1

ALARM CLOCK CHIP

NS. MM5375AA. Six Digits.
With full Data. New!

$2.49 each

MOTOROLA 7805R VOLTAGE REGULATOR

Same as standard 7805 except 750 MA output
TO-220. 5VDC output.

44c each or 10 for $3.95

FULL WAVE BRIDGE

4 AMP. 200 PIV.
69$ 10 FOR $5.75

NOT ASSOCIATED WITH DIGITAL
RESEARCH OF CALIFORNIA, THE
SUPPLIERS OF CPM SOFTWARE.

450 NS! 2708 EPROMS

Now full speed! Prime new units from a major U.S. Mfg. 450 N.S.
Access time. 1 K x 8. Equiv. to 4-1 702 A's in one package.

3 I D« • O Cut 3) ^1

PRICE CUT W

16K STATIC RAM KIT

OUR LATEST COMPUTER KIT!

FULLY S-100 COMPATIBLE!

FULLY STATIC, AT DYNAMIC PRICES!

WHY THE 2114 RAM CHIP?

We feel the 2114 will be the next industry
standard RAM chip (like the 2102 was)
This means price, availability, and
quality will all be good' Next, the 21 14 is
FULLY STATIC 1 We feel this is the ONLY
way to go on the S-100 Buss 1 We've all
heard the HORROR stories about some
Dynamic Ram Boards having trouble
with DMA and FLOPPY DISC DRIVES
Who needs these kinds of problems?
And finally, even among other 4K Static
RAM's the 2114 stands out' Not all 4K
static Rams are created equal! Some of
the other 4K s have clocked chip enable
lines and various timing windows Just at
critical as Dynamic RAM's. Some of our
competitor's 16K boards use these
"tricky'' devices. But not us! The 21 14 is
the ONLY logical choice for a trouble-
free, straightforward design.

§35900
COMPLETE KIT

«*

SPECIAL

INTRODUCTORY OFFER!

Buy 2 KITS (32K) for $650

450 NS

Blank PC Board with Documentation

$33.00

LOW PROFILE SOCKET SET - $12.00

ASSEMBLED & TESTED - ADD $30.00

2114s 4K RAM's - 8 FOR $69.95

KIT FEATURES:

1 Addressable as four separate 4K
Blocks

2 ON BOARD BANK SELECT circuitry
(Cromemco Standard!) Allows up to
512K on line!

3 Uses 2114 (450NS) 4K Static Rams.

4. ON BOARD SELECTABLE WAIT
STATES

5. Double sided PC Board, with solder
mask and silk screened layout Gold
plated contact fingers.

6. All address and data lines fully
buffered.

7 Kit includes ALL parts and sockets

8 PHANTOM is jumpered to PIN 67

9 LOW POWER: under 2 amps TYPICAL
from the *8 Volt Buss.

10. Blank PC Board can be populated as
any multiple of 4K

SUPER SPECIAL: BUY 32 KITS (512 KILOBYTES) (8-64K BANKS) for $ 9,995 00

NATIONAL SEMICONDUCTOR

JUMBO CLOCK MODULE

MA1008A
BRAND NEW

2 FOR
113

IACXFMH $1 95)

FEATURES

• FOUR JUMBO '/> INCH LEO DISPLAYS

• 12 MR REAL TIME FORMAT

• 24 HR ALARM SIGNAL OUTPUT

• 50 OR 60 Hz OPERATION

• LEO BRIGHTNESS CONTROL

• POWER FAILURE INDICATOR

• SLEEP & SNOOZE TIMERS

• DIRECT LED DRIVE (LOW RFI)

• COMES WITH FULL DATA

ASSEMBLED) NOT A KIT!

ZULU VERSIONI

We have ■ limited number of the 24 HR Real
time version ot this module in stock

•MA100SD — $9 95

PERFECT FOR USE
WITH A TIMEBASE.

COMPARE AT UP TO TWICE
OUR PRICE!

MANUFACTURER'S CLOSEOUT'

Digital Research Corporation

_ (OF TEXAS) r

P. O. BOX401247K GARLAND, TEXAS 75040 • (214) 271 2461

-»■ .

SALE!

1N4148 DIODES. SILICON.

Same as 1N914. New,

factory prime, Full Leads.

100 FOR $2

1000 FOR $17.50

New! REAL TIME
Computer Clock Chip

N.S. MM531 3. Features
BOTH 7 segment and
BCD outputs. 28 Pin

DIP. $4.95 with Data

MICRO-MINI TOGGLE SWITCH

990

EACH

SPDT. By RAYTHEON
MADE IN USA! WITH HDWR

6 FOR $5

TERMS: Add 30$ postage, we pay balance. Orders under
$15 add 75$ handling. No COD. We accept Visa, Master-
charge, and American Express cards. Tex. Res. add 5% Tax.
Foreign orders (except Canada) add 20% P & H. 90 Day
Money Back Guarantee on all items.

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DEfiLEf

ICTORU

Phoenix AZ

Bits & Bytes Computer Shop has microcom-
puter systems for the small businessman and
hobbyist and an experienced technical staff
We carry: Vector Graphic, Imsai, Integrand,
North Star and others Bits & Bytes Computer
Shop, 6819 North 21st Ave., Phoenix AZ
85015, 242-2507.

Los Angeles CA

Featuring PolyMorphic, North Star, Imsai,
Cromemco, Extensys, Speechlab products
and Poly-88 Users Croup software exchange
All products 10-20% off list We won't be
undersold! A-A-A-A Discount Computer
How's, 1477 Barrington, Suite 17, Los Angeles
CA 90025, 477-8478.

Palo Alto CA

Systems available for immediate delivery
word processing, multiprogramming, multi-
user work in process, business; medical/den-
tal billing and accounts receivable Software
and hardware guaranteed Byte of Palo Alto,
2233 El Camino Real, Palo Alto CA 94306,
327-8080.

Chicago IL

Staffed by computer professionals Largest
selection of books and magazines in the
Chicago area Specialists in CP/M, Apple
Computer and Alpha microsystems Data
Domain of Schaumburg, Plaza de las Flores,
1612 E. Algonquin Rd., Schaumburg IL 60195,
397-8700.

Naperville IL

Discount Prices: Creed Teletypes, optical
scanners. Solid State Music products, In-
tegrand mainframes, Vista floppy-disk
systems, many other items, complete hard-
ware and software systems Wilcox Enter-
prises, 25Wl78-39th St., Naperville IL 60540,
420-8601.

Prairie Village KS

Computer systems for small business applica-
tions, featuring production and inventory
control, accounts rec & pay., financial plan-
ning & general ledger. 20 yrs experience
Data Management Enterprises, 4900 Somerset
Drive, Prairie Village KS 66207, 381-6823.

Dealers: Listings are $15 per month in prepaid quarterly payments, or one yearly payment of $150.
also prepaid Call Marcia at 603-924-3873 or write Kilobaud. Ad Dept . Peterborough NH 03458

Syracuse NY

We stock: Apple, Commodore PET, KIM,
North Star, Cromemco. Imsai, TDL, Vector
Graphic, Heuristics, Lear Siegler, Netronics
Elf, books, magazines, parts and supplies
Computer Shop of Syracuse, Inc., 3470 Erie
Blvd. East, DeWitt NY 13214, 446-1284.

Hickory NC

Turnkey microcomputer systems for profes-
sional, business and industrial applications,
featuring Imsai (and the fabulous VDP-80)
Custom software, expert service and sound
advice from DP specialists Microcomputer
Services, 108-110 Arcade Building, Hickory
NC, 462-1401.

Akron OH

We've got it all Business systems Personal
systems Software packages Custom pro-
gramming. Terminals Printers. Service and
books Easy freeway access 11 AM to 7 PM
Monday-Saturday The Basic Computer Shop;
Fairlawn Plaza, 2671 West Market St., Akron
OH 44313,867-0808.

York PA

Personal and small-business systems Com-
ponents and peripherals Books, magazines,
information Hobbyists welcome Vi block
from Business 83 at Iron Bridge C.Y.C. Co., 51
Hamilton Ave., York PA 17404, 854-0481.

Memphis TN

Computerlab of Memphis — Now open Serv-
ing the mid-South with a complete line of the
most popular systems Computerlab, 627
South Mendenhall Rd., Memphis TN 38117.

Houston TX

Bare boards, kits, small systems, multiuser
systems, custom hardware design, software
for business or hobby, nationwide consulting
available Please call Houston Computer
Mart, 8029 Gulf Freeway, Houston TX 77017,
649-4188.

Houston TX

Supplier of microcomputer components and
systems for business and pleasure Business
systems delivered ready to run, hardware and
software Also design computerized machine
logic controllers Musgrove Engineering, 9547
Kindletree Dr., Houston TX 77040, 466-3486.

Richland WA

Apple, North Star, Ohio Scientific All prod-
ucts listed in Byte Shopper, classes, literature,
electronic parts, repair services. Custom de-
sign/consulting in both hardware and soft-
ware Ye Olde Computer Shoppe, inc., 1301
George Washington Way, Richland WA
99352, 946-3330.

Is your city listed?

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Hit

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comes to standing on the bookshelf. Try the Kilobaud
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only for Kilobaud, but also for 73 Magazine . . . and for Per-
sonal Computing, Radio Electronics, Interface Age, and
Byte. Ask for whatever stickers you want with your box
order. Hams may want our labels for CQ, QST or Ham
Radio. They hold a full year of Kilobaud ... or 73. Your
magazine library is your prime reference, keep it handy and
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box is $2.00, 2 boxes are $3.00 and eight boxes are $10.00.
Be sure to specify which labels we should send. Have your
credit card handy and call our toll-free order number
800-258-5473, or use the order card in the back of the
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KILOBAUD LIBRARY SHELF BOXES Peterborough, NH 03458

1977 kilobaud Binden

Keep your Kilobauds from being lost or
damaged in these handsomely appointed binders
with rich blue covers and gold lettering. Each
binder holds 12 issues, making an EXCELLENT
REFERENCE HANDBOOK. Several binders
form a quality library you can be proud of.

Order yours today . . . only $6.50 each
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2 for

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Be sure to include check or detailed credit card information

143

KB BOOK HOOK

• HOBBY COMPUTERS ARE HERE!-

BK7322— If you want to come up to speed
on how computers work . . . hardware and
software . . . this is an excellent book. It
starts with the fundamentals and explains
the circuits, the basics of programming,
along with a couple of TVT construction
projects, ASCII-Baudot, etc. This book has
the highest recommendations as a teach-
ing aid for newcomers. $4.95.*

• THE NEW HOBBY COMPUTERS-
BK7340— This book takes it from where
"Hobby Computers Are Here!" leaves off,
with chapters on Large Scale Integration,
how to choose a microprocessor chip, an
introduction to programming, low cost I/O
for a computer, computer arithmetic,
checking memory boards, a Baudot moni-
tor/editor system, an audible logic probe
for finding those tough problems, a ham's
computer, a computer QSO machine . . .
and much, much more! $4.95*

• INTRODUCTION TO MICROPROCES-
SORS— BK1032— by Charles Rockwell of
MICROLOG is an ideal reference for the
individual desiring to understand the
hardware aspects of microprocessor sys-
tems. Describes the hardware details of
computer devices in terms the beginner
can understand, instead of treating the
micro chip as a "black box." Specific
systems are not described and program-
ming is only briefly discussed. $17.50 US
and Canada, $20 elsewhere.*

• BASIC NEW 2ND EDITION— BK1081 —
by Bob Albrecht. Self-teaching guide to
the computer language you will need to
know for use with your microcomputer.
This is one of the easiest ways to learn
computer programming. $4.95.*

• SCIENTIFIC RESEARCH INSTRU-
MENTS' BASIC SOFTWARE LIBRARY is a

complete do-it-yourself kit. Written in
everybody's BASIC immediately execut-
able in ANY computer with 4K, no other
peripherals needed. Volume I contains
business and recreational programs and
is 300 pages. Volume II is 260 pages and
contains math, engineering, statistics and
plotting programs. Volume III contains
money managing, advanced business pro-
grams such as billing, A/R, inventory,
payroll, etc. Volume IV contains general
purpose programs like loans, rates, retire-
ment, plus games: Poker, Enterprise (take
charge while Capt. Kirk is away), Football
and more! Volume V is filled with experi-
menter's programs including games, pic-
tures and misc. problems like "logic." Vol-
ume I — LB1002— & Volume II — LB1003—
$24.95* each, Volume III — LB1004—
$39.95*, Volume IV— LB1005— & Volume
V— LB1006— $9.95* each, Volume VI—
LB1007— $49.95*, Volume VII — LB1008—
$39.95.*

• MICROPROCESSOR INTERFACING
TECHNIQUES— BK1037 — by Austin
Lesea & Rodnay Zaks will teach you how

HOBBY

compu"

[BAUD <ifcAi

RATE! entf)

HDBBV ,
COmPUTF

"""OOUCTIOH

Pr*rl m

"^oPHocessovs

M 'CfK)LOC

T 2X MR1T "

COOKBOOK

MICROPROCESSOR

XK^OMZZL INTERFACING
1 TECHNIQUES

VOLUME

to interconnect a complete system and in-
terface it to all the usual peripherals. It
covers hardware and software skills and
techniques, including the use and design
of model buses such as the IEEE 488 or
S100. $9.95*

• TTL COOKBOOK— BK1063— by Donald
Lancaster. Explains what TTL is, how it
works, and how to use it. Discusses prac-
tical applications, such as a digital count-
er and display system, events counter,
electronic stopwatch, digital voltmeter,
and a digital tachometer. $8.95.

• CMOS COOKBOOK— BK1011— by Don
Lancaster. Details the application of
CMOS, the low power logic family suitable
for most applications presently dominat-
ed by TTL. Required reading for every seri-
ous digital experimenter! $9.95.*

• TVT COOKBOOK— BK1064— by Don
Lancaster, describes the use of a stan-
dard television receiver as a microproces-
sor CRT terminal. Explains and describes
character generation, cursor control and
interface information in typical, easy-to-
understand Lancaster style. $9.95.

• THE "COMPULATOR" BOOK— BUILD-
ING SUPER CALCULATORS & MINICOM-
PUTER HARDWARE WITH CALCULATOR

CHIPS— BK1012— by R. P. Haviland, pro-
vides ideas, design info and printed circuit
boards for calculator chip projects, mea-
sure time, tie in with a Teletype to create a
virtually infinite memory system, and
countless other functions. $7.95.*

• BASIC COMPUTER GAMES— BK1074—
Okay, so once you get your computer and
are running in BASIC, then what? Then
you need some programs in BASIC, that's
what. This book has 101 games for you,
from very simple to real buggers. You get
the games, a description of the games,
the listing to put in your computer and a
sample run to show you how they work.
Fun. Any one game will be worth more
than the price of the book for the fun you
and your family will have with it. $7.50.*

• WHAT TO DO AFTER YOU HIT RETURN

— BK1071 — PCC's first book of computer
games ... 48 different computer games
you can play in BASIC . . . programs, de-
scriptions, many illustrations. Lunar Land-
ing, Hammurabi, King, Civel 2, Qubic 5,
Taxman, Star Trek, Crash, Market, etc.
$8.00.*

• KILOBAUD CODING SHEETS Kilobauds
dozen or so programmers wouldn't try to
work without these handy scratch pads
which help prevent the little errors that can
cost hours and hours of programming
time. Available for programming is
Assembly/Machine Language (PD1001)
which has columns for address, instruc-
tion (3 bytes), source code (label, op code,
operand), and comments; and for BASIC
(PD1002) which is 72 columns wide. 50
sheets to a pad. $2.39.*

?. u G ^° rC ? e L card m the back of thls m agazine or itemize your order on a separate piece of paper and mail to
Kilobaud Book Department • Peterborough NH 03458. Be sure to include check or detailed credit card information

For orders under $10.00, add $1.00 shipping and handling.

FOR TOLL FREE ORDERING CALL 1-800-258-5473

KB BOOK MOOK

SPECIAL:

PRE-PUBLICATION OFFER

(orders will be filled on

;-in, first-out basis)

n Kroto mput9r

• HOW TO BUILD A MICROCOMPUTER—
AND REALLY UNDERSTAND IT-BK7325
—by Sam Creason. The electronics hobby-
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$9.95.*

• PROGRAMMING IN PASCAL-BK1140
—by Peter Grogono. The computer pro-
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concepts of structured programming
which had been defined by Edsger Dijkstra
and C. A. R. Hoare. As such it is a landmark
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• MICROPROCESSOR LEXICON-ACRO-
NYMS AND DEFINITIONS— BK1137—
Compiled by the staff of SYBEX is a conve-

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part numbers and their definitions, S-100
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• INSTANT BASIC-BK1131-by Jerald
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language, here, finally, is a new book to
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• YOUR HOME COMPUTER-BK1172-
by James White is an introduction to the
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SOFTWARE

KILOBAUD

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available

• PERSONAL WEIGHT CONTROL/BIO-
RHYTHMS by Microcosm. A must for the
diet-conscious. Our Biorhythm program
charts physical, emotional and intellec-
tual highs and lows!

• SPACE TREK by KB1. This game wil
challenge the most skillful and careful
player. You are the commander of the

•"BEGINNER'S BACKGAMMON/KENO by
Fred Schild and KB1. You'll never need a
backgammon companion again. The Keno
program is Las Vegas at home, and you

• a BASIC b LUNAR LANDER/INTERMEDIATE
LUNAR LANDER by KB1 . You are forced to
make a manual landing, and the utmost
concentration is a must for you to touch

fMORTGtGE WITH PREPAYMENT OP-

TION/FINANCIER by Microcosm. Before
you go to the bank you'll need to check
your computer; our mortgage program wiH
qive you the information you'll need.
Financier is actually three programs in
one, and it's bound to make you a financial

wizard. _ XAIIl ^

• GOLF/CROSS-OUT by Wilford

Niepraschik and David Dillehay. The pros
would love this one . . . golf on a com-
puter. Play the game anytime— rain or
shine. Take your choice of clubs and
angle Cross-Out is the old peg dilemma. It
tests your skill and rates your effort after

each try

• ELECTRONICS I by Rick Morel. This is
actually a group of five different programs.
Design coils for radio circuits, calculate
component values, design preamplifiers.
These programs are a great help around

the lab and are wonderful teaching aids.

• HAM PACKAGE I by Rick Morel/D. A.
Lien A must for any workshop or ham-
shack. This group of eight programs will be
of frequent help to any experimenter or
ham operator.

• CASINO I by Charles M. Stuart. If you
plan to visit Las Vegas someday, this pro-
gram will prepare you; if not you'll have a
ball learning every combination you could
play at the MGM Grand Hotel.

• CASINO II by Charles M. Stuart. You
play this game under the same house rules
as the casinos in Vegas. With this game,
once you have mastered it, it will enable
you to walk away from any craps table a
winner. You'll end up paying for your com-
puter using this game.

vnn rntrniniuni v . ...w — , -

FOR FURTHER INFORMATION AND DESCRIPTIONS TURN TO PP. 112 & 113

av/aiiahip are used BASF digitally certified. **-*-* inthokiir.ha.iri I ah and are beina readied for publication. Use the coupon on pg. 113 to

MORE TO COME As of this printing, over 200 program cassettes have been tested m the K. obaud L h ab j^ n ° ^^ e t a ° dy including: small business accounting, check-

others. .

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WHO'S BEHIND 1HE

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WST /MOMH'S /MYSTERY RE4DER

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Biorhythms— $7.95
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BK1071 What To Do After You Hi
Return— $8.00

BK1172 Your Home Computer—
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you can uyz in your bu>inc»

ready to go noco!

a t ActUkmw

Our programs will let you realize

We developed these programs because we needed them
in our businesses, and, try as we might, could not purchase
them. They're on-line now, working for us and others around
the country.

As users ourselves we know the problems from your
perspective — not just as a manufacturer of software. The
bugs are out and they' re ready now to go to work helping make
your life easier, keeping you in better control of your business.

Our first four program packages are: • Apartment
Management • Cash Register • Inventory • Payroll

Here's a typical program

To give you an idea of the thoroughness of these pro-
grams, here's a summary of what the inventory package does
for you. Gives a detailed listing of items in inventory and
itemizes all goods sold from inventory, including which sales
person sold what, when it sold and for how much . . . recaps on
one sheet this same inventory activity information . . . investi-
gates and changes any information in inventory, on request . . .
prints list of items to be re-ordered . . . provides profit analysis
comparing sales personnel and/or various products. And it
can be inter-connected with our cash register package as well,
for total program management.

Each of our initial programs is conceived, proven and
offered with this same exacting thoroughness and attention to
detail.
We stay with you after the sale

We're in this for the long haul and our support
program is dedicated to that objective. Registered
program owners receive:

Master Charge and Via cards accepted

the full potential of your hardware

• Periodic newsletters which include users' ideas and
information exchange, plus tips to owners on further increas-
ing benefits of the package through updated operational flexi-

• Availability of software technicians to provide im-
mediate answers to questions, via phone or mail.

• Customer rewrites and adaptations available on re-
quest, at added cost.

CBASIC-2 free

It takes the world's most powerful commercial basic to
run our programs and we deliver it to you free.

Each of our program packages contains a disk with
CBASIC-2 Compiler, CBASIC-2 Run Command and your
Graham-Dorian software programs in INT and BAS file form.
You also receive User's Manuals and Hard Copy Source List-
ing. At a price which pays for itself!

CBASIC-2 was developed and written by Software Sys-
tems, the people who wrote CBASIC, and includes many
powerful enhancements*AII systems are compatible with any
Z-80 or 8080 CP/M® system. They are deliverable in standard
eight-inch disk — either double or single density — or mini-
floppy disk.

Give us a call or fill out the Reader Service Card in this
issue. We promise a response within 24 hours of receipt.

That's the kind of information service we expect,
and know you do too.

CBASIC-2 may be purchased separately

from Graham- Dorian Software Systems for $89.95.

Graham-Dorian Software Systems

A Division of Graham-Dorian Enterprises

211 N. Broadway / Wichita, Ks. 67202 / (316) 265-8633

11B

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